Macroeconomics

Zooming out from the individual to the whole

Microeconomics studies individual pieces of the economy - a single buyer, one firm, or one market. Macroeconomics steps back to study the economy as a whole: the total value of everything a nation produces, the average level of prices, the share of workers without jobs, and the pace at which living standards rise. It asks why entire economies boom and slump together, and what governments and central banks can do about it.

The shift in scale matters because the whole is not simply the sum of its parts. A single household spending less is thrift; every household cutting spending at once can shrink the economy and cost people their jobs. This surprising result - that what is sensible for one actor can be harmful for all at once - is called the paradox of thrift, and it is a hint that macroeconomics needs its own tools.

The three big questions

Nearly everything in this course serves three goals that economists use to judge how an economy is doing:

1. Output and growth - Is the economy producing more goods and services over time? We measure this with gross domestic product (GDP) and its growth rate.
2. Employment - Are the people who want to work able to find jobs? We measure this with the unemployment rate.
3. Stable prices - Is the overall price level roughly steady, avoiding high inflation or falling prices? We measure this with the inflation rate.

An economy that grows steadily, keeps unemployment low, and holds inflation mild is doing its job. When one of these breaks down - a recession throws people out of work, or prices spiral upward - macroeconomic policy tries to bring it back toward balance.

Stocks versus flows

A recurring distinction is between a stock, a quantity measured at a single point in time, and a flow, a quantity measured over a period. Your bank balance today is a stock; your monthly income is a flow. In macroeconomics, the national debt is a stock (a total owed on a given date), while the annual budget deficit is a flow (the shortfall added each year). GDP itself is a flow - output produced per year. Confusing the two is a common error, so it is worth fixing the idea early.

Positive and normative, again

As in all economics, we separate positive statements (testable claims about what is - "unemployment rose to 5% last quarter") from normative statements (value judgments about what ought to be - "the government should cut unemployment even at the cost of higher inflation"). Data can settle the first; only values can settle the second. Keeping them apart keeps analysis honest.

An economy as a loop

The circular-flow model is the simplest picture of how a whole economy fits together. In its basic form, two groups meet in two markets. Households own the resources - labor, land, and capital - and sell them to firms in the resource (factor) markets, earning wages, rent, and profit. Firms use those resources to make goods and services, which they sell back to households in the product markets. Money flows one way around the loop; goods, services, and resources flow the other way.

The key insight is that every dollar of spending by one party is a dollar of income for another. When you buy a coffee, your spending becomes the cafe's revenue, which becomes wages for its workers and profit for its owner. Follow the loop all the way around and you reach a fundamental identity: total income equals total expenditure equals the value of total output. This is why, as the next module shows, GDP can be measured either by adding up all spending or by adding up all income - the two must match.

Leakages and injections

The real economy is not a perfectly closed loop, because money can leave the flow and re-enter it elsewhere. Money that leaves the domestic spending stream is a leakage; money that enters it is an injection.

When households save, that income is not spent on domestic goods right away - it leaks out - but banks channel it back as investment when firms borrow to build factories. Taxes leak out to the government, which injects them back through spending. Money spent on imports leaks abroad, while exports inject foreign spending in. When total injections equal total leakages, the flow is balanced and the economy is at rest; when injections exceed leakages, spending and output tend to expand.

Why the model matters

The circular flow is more than a diagram. It shows that output, income, and spending are three views of the same thing, it names the six forces (S, T, M, I, G, X) that drive the economy up or down, and it previews the accounting behind GDP. Keep the loop in mind and later topics - the spending multiplier, trade balances, and fiscal policy - will feel like natural extensions of a picture you already understand.

What GDP is - word by word

Gross domestic product (GDP) is the market value of all final goods and services produced within a country in a given period. Every phrase does work:

• Market value - we add up dissimilar goods (cars, haircuts, apples) by their prices, giving a common dollar measure.
• Final - we count only goods sold to their end user, not intermediate goods resold or built into something else, to avoid double counting.
• Produced - GDP counts new production, not the resale of used goods or purely financial transactions like buying stocks.
• Within a country - GDP is about location of production, regardless of who owns the firm.
• In a period - usually a year or a quarter; GDP is a flow.

The expenditure approach

The most common way to compute GDP is to add up all the spending on final goods and services, sorted into four categories:

GDP = C + I + G + NX

• Consumption (C) - household spending on goods and services; the largest component.
• Investment (I) - business spending on capital (machines, buildings) plus new housing and changes in inventories. Note: buying stocks is not investment here.
• Government purchases (G) - federal, state, and local spending on goods and services. It excludes transfer payments like Social Security, which are not payments for production.
• Net exports (NX) - exports minus imports, NX = X - M. We subtract imports because C, I, and G include spending on foreign-made goods that were not produced here.

Worked example

Suppose a country reports, for one year (in billions of dollars): consumption $14,000; investment $3,500; government purchases $4,000; exports $2,100; imports $2,600. Compute GDP.

Net exports NX = X - M = 2,100 - 2,600 = -500
GDP = C + I + G + NX = 14,000 + 3,500 + 4,000 + (-500)
GDP = $21,000 billion (that is, $21 trillion)

The net-export term is negative here because the country imports more than it exports - a trade deficit - which reduces measured GDP relative to what domestic spending alone would suggest.

Avoiding double counting

Why count only final goods? Imagine a baker buys $0.40 of flour to make bread sold for $2.00. If we counted both the $0.40 flour and the $2.00 loaf, we would count that flour twice - once on its own, once inside the loaf. Counting only the final $2.00 loaf captures the full value exactly once. An equivalent method sums the value added at each stage (the seller's price minus the cost of its inputs); the total value added always equals the final sale price.

The other side of the ledger

Because every dollar spent on final output becomes someone's income, GDP can be measured a second way: the income approach adds up all the income earned in production instead of all the spending on it. The main categories are wages and salaries (compensation of employees), rent, interest, and profits, with a couple of accounting adjustments for depreciation and taxes on production. In principle the income approach and the expenditure approach give the identical total - they are two ways of counting the same circular flow. In practice small measurement gaps appear, reported as a "statistical discrepancy," but the two are conceptually equal.

A family of related measures

Several close cousins of GDP appear in the news, and it helps to keep them straight:

• Gross national product (GNP) counts output by a country's residents wherever it is produced, rather than output produced within its borders. GDP is about location; GNP is about ownership.
• Net domestic product (NDP) is GDP minus depreciation (the wearing out of capital), measuring output net of the capital used up making it.
• Real GDP per capita - real GDP divided by population - is the single best rough gauge of average living standards, and the focus of the growth module.

What GDP leaves out

GDP is the headline measure of an economy's size, but its designers never intended it as a measure of welfare, and it misses a great deal:

• Non-market production - unpaid housework, childcare, and volunteering produce real value but are not sold, so GDP ignores them.
• The underground economy - legal work paid in cash and illegal activity go largely uncounted.
• Distribution - GDP is a total; it says nothing about whether the income is shared widely or concentrated in a few hands.
• Leisure and non-material well-being - more output produced by working longer hours may not mean people are better off.
• Environmental costs - GDP counts the output from polluting activity but not the damage to air, water, or climate; it can even rise when we spend to clean up disasters.

Why we still use it

Despite these gaps, GDP remains indispensable. It correlates strongly with things people plainly value - life expectancy, literacy, and access to goods and services all tend to rise with real GDP per capita. The mature view is to treat GDP as a powerful but partial gauge: excellent for tracking the size and cycles of production, but best paired with other indicators when the question is human well-being rather than economic output.

Why we need two GDPs

Because GDP is measured in money, it can rise for two very different reasons: the economy produces more stuff, or the same stuff costs more. To track genuine changes in output we must separate quantity from price. Nominal GDP values output at current-year prices, so it mixes the two. Real GDP values output at the prices of a fixed base year, holding prices constant so that any change reflects a change in real quantities produced.

Worked example: a simple economy

Imagine an economy that produces only bread. Let year 1 be the base year.

Nominal GDP jumped from $1,000 to $1,440, a rise of 44 percent - but part of that is just higher prices. Real GDP uses the base-year price of $10 for both years: year 2 real GDP is 120 loaves x $10 = $1,200. So real output rose from $1,000 to $1,200, a real gain of (1,200 - 1,000) / 1,000 = 20 percent. In the base year, nominal and real GDP are always equal by construction.

The GDP deflator

The gap between nominal and real GDP is itself a useful price measure. The GDP deflator is defined as:

GDP deflator = (Nominal GDP / Real GDP) x 100

For year 2: deflator = (1,440 / 1,200) x 100 = 120. The deflator equals 100 in the base year (since nominal equals real), so a reading of 120 means prices overall are 20 percent higher than in the base year - matching the price rise from $10 to $12. The deflator is a price index: a number that tracks the overall price level relative to a base of 100.

Computing inflation from the deflator

The inflation rate between two years is the percentage change in a price index:

Inflation = ((Index this year - Index last year) / Index last year) x 100

If the deflator rises from 120 to 126, inflation is (126 - 120) / 120 = 6 / 120 = 5 percent. Any price index works the same way, which is exactly how the Consumer Price Index in the next lesson is used.

Pricing a typical household's basket

The most widely watched price measure is the Consumer Price Index (CPI), which tracks the cost of a fixed market basket of goods and services bought by a typical urban household - food, housing, transportation, medical care, and more. Statistical agencies survey households to fix the basket, then re-price that same basket month after month. Because the basket is held constant, changes in its cost reflect changes in prices, not in what people buy.

Building the index

The CPI expresses the basket's cost relative to a base period set at 100:

CPI = (Cost of basket this year / Cost of basket in base year) x 100

Worked example

Suppose a household's basket contains 10 kilograms of rice and 5 shirts. Prices are:

Base-year basket cost = (10 x $2) + (5 x $20) = 20 + 100 = $120.
Current-year basket cost = (10 x $3) + (5 x $24) = 30 + 120 = $150.
CPI for 2020 = (150 / 120) x 100 = 125.

Since the base-year CPI is 100 by definition, a 2020 CPI of 125 means the basket costs 25 percent more than in 2015. The inflation rate from 2015 to 2020 is therefore (125 - 100) / 100 = 25 percent over that span. Year-over-year, if the CPI rises from 125 to 130, inflation for that year is (130 - 125) / 125 = 5 / 125 = 4 percent.

Using the CPI to compare dollars over time

The CPI lets us convert a past dollar amount into today's dollars to compare purchasing power:

Value in today's dollars = Past amount x (CPI today / CPI then)

A $10 wage when the CPI was 100, compared at a CPI of 125, is worth 10 x (125 / 100) = $12.50 in today's prices - so a nominal wage that stayed at $10 actually lost purchasing power.

Why the CPI overstates inflation

Because the basket is fixed, the CPI tends to overstate the true rise in the cost of living for several reasons:

• Substitution bias - when one good gets pricier, shoppers buy less of it and more of substitutes, but the fixed basket keeps the old quantities, overstating the pain.
• Quality change - if a product improves, part of a price rise pays for more quality, not pure inflation.
• New goods - genuinely new products enter the basket only with a lag, so early benefits are missed.

These biases matter because the CPI is used to adjust wages, pensions, and tax brackets. The GDP deflator (previous lesson) and the CPI usually move together but can differ, since the deflator covers all domestic output while the CPI covers a fixed consumer basket that includes imports.

Sorting the adult population

To measure unemployment, statistical agencies survey households and place every working-age adult into one of three boxes:

• Employed - people who did any paid work in the survey period (or were temporarily away from a job).
• Unemployed - people who have no job, are available to work, and have actively looked for work recently.
• Not in the labor force - everyone else: full-time students, retirees, homemakers, and those who are not looking.

The crucial grouping is the labor force, defined as the employed plus the unemployed - that is, everyone who is either working or actively seeking work. People not in the labor force are simply not counted in the numerator or denominator of the unemployment rate.

The two key formulas

Unemployment rate = (Unemployed / Labor force) x 100
Labor force = Employed + Unemployed
Labor force participation rate = (Labor force / Working-age population) x 100

Worked example

Suppose a country has, in millions: 152 employed, 8 unemployed, and a working-age (adult) population of 250.

Labor force = 152 + 8 = 160 million
Unemployment rate = 8 / 160 = 0.05 = 5 percent
Labor force participation rate = 160 / 250 = 0.64 = 64 percent

Notice the 90 million people (250 - 160) who are neither employed nor looking do not appear in the unemployment rate at all. The unemployment rate is a share of the labor force, not of the whole population.

Why the rate can mislead

The headline number leaves out two important groups. Discouraged workers want a job but have given up actively looking, so they are counted as "not in the labor force" rather than unemployed - which pushes the measured rate down even though joblessness is real. The underemployed - people working part-time who want full-time work, or working far below their skill level - count as fully employed, so the official rate misses the shortfall in hours. For these reasons, agencies publish broader measures alongside the standard rate, and analysts watch the participation rate to see whether people are entering or leaving the labor force entirely.

Three kinds of unemployment

Not all unemployment has the same cause or cure. Economists sort it into three types:

• Frictional unemployment - short-term joblessness as people move between jobs or enter the labor market. A new graduate searching for a first job, or someone who quit to find a better fit, is frictionally unemployed. It reflects the normal time it takes to match workers to jobs and is largely unavoidable, even healthy.
• Structural unemployment - longer-term joblessness from a mismatch between the skills or locations workers have and the jobs available. When technology or trade eliminates an industry, displaced workers may lack the skills the growing sectors need. Retraining and relocation help, but structural unemployment can persist.
• Cyclical unemployment - joblessness caused by the downturn phase of the business cycle. In a recession, total spending falls, firms cut production, and they lay off workers regardless of their skills. This is the type that macroeconomic policy most directly tries to reduce.

The natural rate of unemployment

Because frictional and structural unemployment are always present - there are always people between jobs and always some mismatch - the unemployment rate never falls to zero even in a healthy economy. The natural rate of unemployment is the sum of frictional and structural unemployment: the rate that prevails when the economy is producing at its sustainable capacity and cyclical unemployment is zero.

Natural rate = frictional + structural unemployment
Actual rate = natural rate + cyclical unemployment

When economists say the economy is at full employment, they do not mean zero unemployment; they mean the actual rate equals the natural rate, with no cyclical unemployment. During a boom the actual rate can dip below the natural rate (labor markets are unusually tight); in a recession it rises above it as cyclical unemployment appears.

Worked reasoning

Suppose an economy's natural rate is 4.5 percent (say 3 percent frictional and 1.5 percent structural) and the actual unemployment rate is 7 percent. Then cyclical unemployment is 7 - 4.5 = 2.5 percent, the part attributable to a weak economy. If a recovery restores full employment, that 2.5 points should disappear while the 4.5 percent natural rate remains. This decomposition tells policymakers how much of a jobs problem is a demand shortfall (treatable with stimulus) versus a structural issue (needing training and time).

The costs of unemployment

Unemployment is costly beyond lost income. For the economy it means output is below potential - goods and services that are never produced. For individuals it can bring loss of skills, health problems, and hardship for families. These human and economic costs are why keeping cyclical unemployment low is a central goal of macroeconomic policy.

Three words for changing prices

Inflation is a sustained increase in the overall price level - not a one-time jump in a single good, but a broad, ongoing rise measured by an index like the CPI. Two related terms matter: deflation is a sustained fall in the price level (a negative inflation rate), and disinflation is a slowdown in the rate of inflation (prices still rising, but more slowly). Note that a rise in one price - say gasoline - is not inflation unless the general level of prices is rising.

Two causes: demand-pull and cost-push

Inflation can originate on either side of the market.

• Demand-pull inflation arises when total spending grows faster than the economy's ability to produce - "too much money chasing too few goods." A booming economy, rapid growth in the money supply, or a surge in government spending can pull prices up as buyers compete for limited output.
• Cost-push inflation arises when the cost of producing goods rises across the board, pushing prices up even without extra demand. A sharp jump in oil prices or wages, or a supply shock like a harvest failure, raises firms' costs and forces higher prices while output may actually fall.

A useful lens is the quantity theory of money, summarized by the equation of exchange M x V = P x Y, where M is the money supply, V its velocity (how often a dollar is spent), P the price level, and Y real output. If velocity and real output are roughly stable, then sustained growth in the money supply (M) translates into a higher price level (P). This is the core reason economists link persistent inflation to excessive money growth.

Why inflation is costly

Mild, predictable inflation is manageable, but inflation imposes real costs:

• Reduced purchasing power - each dollar buys less, so anyone whose income does not keep pace falls behind.
• Menu costs - the resources firms spend constantly changing prices, catalogs, and menus.
• Shoe-leather costs - the effort of economizing on cash that is losing value.
• Distorted decisions - when prices are noisy, it is harder to tell real changes from inflation, muddling saving and investment choices.

Winners and losers

Inflation redistributes wealth, especially when it is unexpected. Borrowers with fixed-rate loans gain, because they repay in dollars worth less than the ones they borrowed, while lenders lose for the same reason. People on fixed incomes or holding cash lose purchasing power. This is why economists distinguish the nominal interest rate (the stated rate) from the real interest rate, which subtracts inflation:

Real interest rate = Nominal interest rate - Inflation rate

If a bank pays 5 percent nominal interest and inflation is 3 percent, the real return is only 2 percent. If inflation unexpectedly hits 6 percent, the real return is negative 1 percent - savers actually lose ground. Because inflation shifts wealth between groups and clouds decisions, keeping it low and stable is a core policy goal.

A short-run trade-off

Two of our headline indicators - unemployment and inflation - turn out to be linked in the short run. The Phillips curve describes an inverse relationship between them: periods of low unemployment tend to come with higher inflation, and periods of high unemployment with lower inflation. The intuition connects directly to the aggregate demand and aggregate supply model from the previous topics. When aggregate demand rises, output expands and unemployment falls, but the tighter economy also pushes prices up - so lower unemployment arrives together with higher inflation. A demand-driven boom trades one for the other.

Why the trade-off breaks down in the long run

The short-run trade-off tempted policymakers to think they could permanently "buy" lower unemployment by tolerating a little more inflation. Experience, especially the stagflation of the 1970s when high unemployment and high inflation appeared together, showed this does not hold for long. The modern view is that there is a long-run Phillips curve that is vertical at the natural rate of unemployment. In the long run, the economy returns to its natural rate no matter what the inflation rate is - just as the long-run aggregate supply curve is vertical at potential output. You cannot lower unemployment below its natural rate permanently simply by accepting more inflation.

The role of expectations

The bridge between the short run and the long run is inflation expectations. Suppose the central bank keeps stimulating demand to hold unemployment below the natural rate. At first, inflation rises and unemployment falls along a short-run Phillips curve. But once workers and firms come to expect higher inflation, they build it into wage demands and price setting. That shifts the entire short-run Phillips curve upward: the same low unemployment now requires even higher inflation to sustain. Push further and the process repeats, producing accelerating inflation with no lasting gain in employment. This is why credible, stable expectations are so prized - they keep the short-run trade-off favorable and inflation anchored.

What it means for policy

The Phillips curve reframes the central banker's job. In the short run, there is a genuine trade-off, so policy can lean against a recession or an inflationary boom. In the long run, there is no trade-off to exploit - only a natural rate set by real factors - so the best a central bank can do for prices is keep inflation low and expectations well anchored. This distinction unites the whole course: aggregate demand policy manages the short-run cycle, while long-run outcomes for output and employment depend on growth and the economy's real structure.

From one market to the whole economy

In microeconomics, a demand curve applies to a single good. In macroeconomics, aggregate demand (AD) is the total quantity of all final goods and services that households, firms, government, and foreigners want to buy at each overall price level. Its components are the same four that make up GDP: consumption (C), investment (I), government purchases (G), and net exports (NX). The AD curve slopes downward, plotting the price level on the vertical axis against real GDP demanded on the horizontal axis.

Why aggregate demand slopes down

The reasons differ from a single market, because when the whole price level changes there is no "other good" to substitute toward. Three effects explain the slope:

• Wealth effect - a lower price level raises the real value of money and savings, so people feel richer and buy more.
• Interest-rate effect - a lower price level reduces the need to hold cash, lowering interest rates, which encourages borrowing and investment.
• Exchange-rate effect - a lower domestic price level (and lower interest rates) makes home-produced goods cheaper relative to foreign goods, raising net exports.

What shifts aggregate demand

Anything that changes total spending at a given price level shifts the whole AD curve. Because AD = C + I + G + NX, a change in any component shifts it:

• Consumption - rises with higher consumer confidence, wealth, or lower taxes; this shifts AD right.
• Investment - rises with business optimism or lower interest rates; shifts AD right.
• Government purchases - more government spending shifts AD right (a lever of fiscal policy).
• Net exports - a boom abroad or a cheaper currency raises exports, shifting AD right.

Be careful to separate a movement along AD (caused by a change in the overall price level) from a shift of AD (caused by any of the factors above). This mirrors the micro distinction between a change in quantity demanded and a change in demand, applied to the whole economy.

The spending multiplier preview

An initial change in spending can shift AD by more than the original amount, because one person's spending is another's income, which is partly spent again. This multiplier effect - explored fully in the fiscal-policy module - is why a change in investment or government spending can have an outsized effect on aggregate demand and output.

Aggregate supply in two time frames

Aggregate supply (AS) is the total quantity of goods and services firms produce at each price level, and its shape depends on the time horizon.

The short-run aggregate supply (SRAS) curve slopes upward: in the short run, some costs (especially wages) are "sticky" and slow to adjust, so a higher price level lets firms sell at higher prices while paying the same wages, raising profits and output. As the price level rises, firms produce more.

The long-run aggregate supply (LRAS) curve is vertical at the economy's potential output (also called full-employment output). In the long run, all prices and wages adjust fully, so output is determined only by real factors - the labor force, the capital stock, and technology - not by the price level. You cannot produce more just because prices are higher once wages catch up.

Macroeconomic equilibrium

The economy is in short-run equilibrium where AD crosses SRAS, setting the price level and real GDP. It is in long-run equilibrium when AD, SRAS, and LRAS all meet at potential output. The gap between actual output and potential output is the output gap:

• A recessionary gap exists when actual output is below potential - a slump, with high cyclical unemployment.
• An inflationary gap exists when actual output is above potential - an overheating boom that pushes prices up.

Tracing shocks

The model earns its keep by showing what shocks do:

• A negative demand shock (say a collapse in confidence) shifts AD left: in the short run both the price level and output fall, opening a recessionary gap and raising unemployment. This is a typical recession.
• A positive demand shock shifts AD right: output and prices rise, and if pushed past potential, an inflationary gap and demand-pull inflation appear.
• A negative supply shock (an oil-price spike) shifts SRAS left: the price level rises while output falls - the painful combination of stagflation (stagnation plus inflation) that leaves policymakers with no easy fix.

Self-correction in the long run

The model also predicts recovery. In a recessionary gap, high unemployment eventually pushes wages and other costs down, which shifts SRAS right and returns output to potential - a slow, automatic self-correction. Whether to wait for this adjustment or to speed it up with active policy is one of the central debates of macroeconomics, and the subject of the policy modules ahead.

The most important number in the long run

Over years and decades, nothing matters more for living standards than economic growth - a sustained rise in real GDP, and especially in real GDP per capita. What looks like a small difference in the annual growth rate compounds into an enormous gap over a lifetime, which is why economists take even fractions of a percentage point seriously.

The rule of 70

A handy shortcut, the rule of 70, estimates how long it takes a growing quantity to double:

Doubling time (years) is approximately 70 / (annual growth rate in percent)

The lesson is dramatic: an economy growing at 7 percent doubles its income in a single decade, while one growing at 1 percent takes a lifetime. Sustained differences in growth are why some nations that were similarly poor a century ago are now vastly richer than others.

Where growth comes from

Long-run growth ultimately comes from rising labor productivity - output per hour worked. Producing more per worker is what lets average incomes rise. Productivity, in turn, grows from a few sources:

• Physical capital - more and better tools, machines, and infrastructure make each worker more productive.
• Human capital - education, skills, and health raise what workers can do.
• Natural resources - land, minerals, and energy help, though they are neither necessary nor sufficient for growth.
• Technological progress - better knowledge and methods let us produce more from the same inputs, and it is the main driver of growth in already-rich countries.

A key idea is diminishing returns to capital: piling on more machines while holding other inputs fixed yields ever-smaller gains, so simply accumulating capital cannot sustain growth forever. Lasting growth in rich economies leans on innovation, which does not run into the same wall.

Institutions and convergence

Good institutions set the stage for all of this: secure property rights, the rule of law, stable government, and openness to trade encourage the investment and risk-taking that growth requires. This framework also suggests the hopeful possibility of convergence - poorer countries can grow faster than rich ones by adopting existing technology and catching up - but only where institutions allow that investment to take root. Where institutions are weak, catch-up stalls.

Growth is not a straight line

Long-run growth trends upward, but the path is bumpy. The business cycle is the recurring pattern of short-run fluctuations in real GDP around its long-run trend. Every cycle has the same four phases, even though their length and depth vary from one cycle to the next.

The four phases

• Expansion - real GDP is rising, unemployment falling, and confidence growing. Most of economic history is spent here.
• Peak - the top of the cycle, where output is highest and the expansion runs out of steam; the turning point into decline.
• Recession (contraction) - a significant, widespread decline in economic activity lasting more than a few months. A common rule of thumb is two consecutive quarters of falling real GDP, though official bodies weigh a broader set of indicators. Unemployment rises during a recession. An especially deep and prolonged recession is called a depression.
• Trough - the bottom of the cycle, where activity stops falling and recovery begins; the turning point back into expansion.

Reading the cycle with indicators

Because turning points are hard to see in real time, economists watch economic indicators classified by their timing:

• Leading indicators tend to change before the overall economy does, offering early warning - examples include new building permits, stock prices, and new orders for capital goods.
• Lagging indicators change after the economy turns, confirming a trend already underway - the unemployment rate is a classic lagging indicator, since firms are slow to hire or fire.
• Coincident indicators move roughly with the economy, such as real GDP and industrial production.

What causes cycles?

Cycles arise from shocks to aggregate demand or aggregate supply - swings in business and consumer confidence, changes in policy, financial crises, or supply disruptions like an oil shock. The AD-AS model from the previous module is the standard tool for analyzing them: a leftward AD shift produces a demand-driven recession, while a leftward SRAS shift produces a supply-driven downturn with rising prices. Understanding the cycle sets up the central policy question of the remaining modules: what, if anything, should government and the central bank do to smooth these fluctuations?

What money does

Money is anything widely accepted in exchange, and economists define it by three functions rather than by its physical form:

• Medium of exchange - you trade it for goods and services, avoiding the awkward "double coincidence of wants" that barter requires.
• Unit of account - prices are quoted in it, giving a common yardstick for value.
• Store of value - it holds purchasing power over time, though inflation erodes this.

Modern money is fiat money: it has value by government decree and common trust, not because it is backed by gold or any commodity. Economists track how much money exists with measures of the money supply, notably M1 (currency plus checkable deposits, the most liquid) and the broader M2 (M1 plus savings deposits and other near-money).

How banks create money

Most money in a modern economy is not printed by the government but created by ordinary banks through fractional-reserve banking. A bank keeps only a fraction of its deposits on hand as reserves and lends the rest out. Those loans are spent and redeposited in other banks, which again keep a fraction and lend the rest, and so on. Each round creates new deposits, expanding the money supply far beyond the original cash.

The money multiplier

The total expansion is captured by the money multiplier, which in the simplest model is:

Money multiplier = 1 / reserve ratio

where the reserve ratio is the fraction of deposits banks hold as reserves. The maximum new money the banking system can create from a fresh deposit is:

Maximum change in deposits = initial deposit x money multiplier

Worked example

Suppose the reserve ratio is 10 percent (0.10) and someone deposits $2,000 in fresh cash into a bank.

Money multiplier = 1 / 0.10 = 10
Maximum new deposits = $2,000 x 10 = $20,000

The initial $2,000 can support up to $20,000 in total deposits across the banking system. Now raise the reserve ratio to 20 percent (0.20): the multiplier falls to 1 / 0.20 = 5, so the same $2,000 supports only $2,000 x 5 = $10,000. A higher reserve ratio means banks lend less of each deposit, so the money supply expands by less. This mechanism is exactly what the central bank influences when it conducts monetary policy.

A note on the real world

The simple multiplier assumes banks lend out every spare dollar and the public redeposits all of it. In practice banks may hold extra reserves and people hold some cash, so the actual multiplier is smaller than 1 / reserve ratio. The principle still holds: fractional-reserve banking lets deposits multiply, and the size of that expansion depends on the reserve ratio and banks' willingness to lend.

The central bank

The Federal Reserve ("the Fed") is the central bank of the United States. It is charged with a dual mandate: to promote maximum employment and stable prices. Beyond steering the economy, it serves as the lender of last resort, supplying emergency funds to solvent banks during a panic to prevent a financial collapse, and it supervises much of the banking system. Its interest-rate decisions are made by the Federal Open Market Committee (FOMC).

The Fed's main tools

The Fed influences the economy by changing the supply of money and the level of interest rates, using three principal tools:

• Open-market operations - buying and selling government bonds. This is the primary day-to-day tool. When the Fed buys bonds, it pays with newly created reserves, increasing the money supply and lowering interest rates; when it sells bonds, it drains reserves, shrinking the money supply and raising rates.
• The discount rate and interest on reserves - the interest rate the Fed charges banks to borrow, and the rate it pays banks on reserves. Adjusting these rates changes banks' incentives to lend and helps steer the key short-term interest rate (the federal funds rate) toward the Fed's target.
• Reserve requirements - the required reserve ratio itself. Lowering it lets banks lend more (raising the money multiplier); raising it does the reverse. This blunt tool is used rarely.

Expansionary versus contractionary policy

Monetary policy comes in two directions, chosen to fit where the economy sits in the business cycle:

The transmission mechanism works through interest rates. In a recession the Fed lowers rates, which makes borrowing cheaper, encouraging firms to invest and households to buy homes and cars. That extra spending shifts aggregate demand right, raising output and employment. To fight inflation the Fed does the opposite: raising rates cools borrowing and spending, shifting AD left and easing price pressures - at the risk of slowing growth.

Strengths and limits

Monetary policy is flexible and fast to enact - the FOMC can change rates at a scheduled meeting without waiting for legislation. But it faces limits. Its effects arrive with a lag of many months. It can lose traction at the zero lower bound, when interest rates are already near zero and cannot be cut much further, as in a severe slump. And pushing too hard on either side risks overshooting - too much stimulus can fuel inflation, too much tightening can trigger a recession. These trade-offs are why central banking is often described as an art as much as a science.

The government's spending-and-tax lever

Fiscal policy is the government's use of spending and taxes to influence the economy. It is set by the legislature and executive - not the central bank - which makes it distinct from monetary policy. Like monetary policy, it works mainly by shifting aggregate demand.

• Expansionary fiscal policy - increasing government spending or cutting taxes to boost aggregate demand during a recession. More spending adds directly to AD; tax cuts leave households and firms more to spend.
• Contractionary fiscal policy - cutting spending or raising taxes to cool an overheating economy and restrain inflation.

The spending multiplier

A change in government spending can raise total output by more than the initial amount, because the money is re-spent again and again around the circular flow. The size of this spending multiplier depends on the marginal propensity to consume (MPC) - the fraction of each extra dollar of income that people spend rather than save:

Spending multiplier = 1 / (1 - MPC)

Worked example

Suppose the MPC is 0.75, meaning people spend 75 cents of every extra dollar. The government increases spending by $100 billion.

Spending multiplier = 1 / (1 - 0.75) = 1 / 0.25 = 4
Maximum increase in GDP = $100 billion x 4 = $400 billion

The first $100 billion is spent by the government; the recipients spend 75 percent of it ($75 billion), whose recipients spend 75 percent of that ($56.25 billion), and so on. The rounds sum to a total of $400 billion. A higher MPC means a bigger multiplier: at an MPC of 0.8 the multiplier is 1 / 0.20 = 5, so the same $100 billion could raise GDP by up to $500 billion. (The saved fraction leaks out each round, which is why a lower MPC gives a smaller multiplier.)

Deficits versus debt - a stock and a flow

Two terms that are constantly confused: the budget deficit is a flow - the amount by which government spending exceeds its tax revenue in a single year (a surplus is the reverse). The national debt is a stock - the total accumulated amount the government owes, the sum of all past deficits minus surpluses. Running a deficit adds to the debt; running a surplus reduces it. A government can shrink its deficit while its debt still grows, as long as it is still spending more than it collects.

Limits and side effects

Fiscal policy is powerful but blunt. It faces time lags: recognizing a downturn, passing legislation, and seeing the effects all take time, so poorly timed policy can arrive too late. Large deficits raise the debt and can cause crowding out, where heavy government borrowing pushes up interest rates and displaces private investment. Some fiscal support is automatic - automatic stabilizers like unemployment benefits and progressive taxes expand in a slump and contract in a boom without any new law, cushioning the cycle on their own. As with monetary policy, economists broadly agree fiscal tools help, while debating their size, timing, and mix.

Why nations trade

Countries trade for the same reason individuals do: comparative advantage. By specializing in what it produces at the lowest opportunity cost and trading for the rest, each nation can consume more than it could in isolation. Trade expands the total economic pie, even when one country is more productive at everything. The gains are real, though they are unevenly distributed, which fuels political debate.

Trade barriers

Governments often limit trade despite these gains. A tariff is a tax on imports; a quota is a legal limit on the quantity imported. A tariff raises the price of imported goods, which helps protected domestic producers and raises revenue for the government, but forces consumers to pay more and typically shrinks total surplus. Trade barriers are usually defended on grounds such as protecting jobs or infant industries, but economists generally find their costs to consumers exceed their benefits to protected groups.

Measuring trade: the balance of trade

The balance of trade is the value of a country's exports minus its imports - the same net-exports term from GDP.

• A trade surplus occurs when exports exceed imports (net exports positive).
• A trade deficit occurs when imports exceed exports (net exports negative).

The broader current account adds income and transfers to the trade balance. A trade deficit is not automatically "bad" - it can reflect strong domestic demand or foreign investment flowing in - but persistent large imbalances are watched closely.

Exchange rates

Trade across borders requires exchanging currencies, and the exchange rate is the price of one currency in terms of another. In a floating system, exchange rates are set by supply and demand for currencies in the foreign-exchange market. Two key terms:

• Appreciation - a currency gains value (buys more foreign currency). A stronger currency makes imports cheaper for domestic buyers but makes the country's exports more expensive abroad.
• Depreciation - a currency loses value. A weaker currency makes exports cheaper and more competitive abroad but raises the cost of imports.

Worked reasoning

Suppose the exchange rate moves from 1 dollar = 100 yen to 1 dollar = 120 yen. The dollar now buys more yen, so the dollar has appreciated (and the yen has depreciated). A Japanese car priced at 2,400,000 yen falls in dollar terms from 2,400,000 / 100 = $24,000 to 2,400,000 / 120 = $20,000, so it is now cheaper for Americans - imports become more attractive. At the same time, a US product priced at $1,000 rises for Japanese buyers from 100,000 yen to 120,000 yen, making US exports harder to sell. This is the core link between currency values and trade flows: a stronger currency tends to widen a trade deficit, a weaker one tends to narrow it. Exchange rates thus tie together everything in this course - trade, interest rates, inflation, and policy - into a single interconnected global economy.