Why Prices Rise

Part 4 showed how a single price gets set: it settles where what buyers want matches what sellers offer. Inflation is what happens when prices across the whole economy rise together.

I’d always thought of inflation as one number in the news. It turned out to be the place where everything earlier in this series meets: money from Part 1, interest rates from Part 2, valuations from Part 3 and markets from Part 4. It’s also where expectations matter most.

As before, I’ve kept the questions I had along the way and what cleared them up.

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What Inflation Is and How It’s Measured

• Price level: the average price of everything people buy.
• Inflation: the price level rising over time. The inflation rate is how fast, usually per year.
• Purchasing power: how much a dollar actually buys. Inflation is purchasing power falling.
• Consumer Price Index (CPI): the main US measure. The Bureau of Labor Statistics tracks the prices of a big basket of what households buy, like rent, groceries, gas, haircuts, cars and doctor visits, weighted by how much people spend on each.
• Core inflation: inflation leaving out food and energy, whose prices swing a lot from month to month.
• Disinflation: inflation slowing down. Prices still rise, just more slowly.
• Deflation: the price level actually falling.

Say Sam’s monthly spending is three things:

Headline inflation is the whole basket: 6.3%. It isn’t the average of the three changes, which would be 13%. Each item counts by how much of the budget it takes. Gas jumped 30%, but it’s a small part of Sam’s spending, so it moves the total less than rent does.

Core inflation leaves out food and energy, so here it’s just rent: 4%. Gas and groceries jump around with weather, wars and harvests. Core shows the slower, stickier trend underneath, which is usually a better guide to where inflation is heading.

Purchasing power fell. Sam needs $1,594 to buy what $1,500 bought a year ago. Each of her dollars buys about 6% less.

Small rates add up. Inflation compounds, like interest does. At 3% a year, prices double in about 24 years, using the rule of 72: 72 ÷ 3 = 24. A dollar kept in cash today buys only half as much a generation from now.

Your inflation isn’t the official number. The CPI is an average basket. If you rent in an expensive city and don’t drive, your own inflation could be well above or below it.

As of September 2026, US consumer prices were 3.7% higher than a year earlier, well above the Fed’s 2% goal.

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What Causes It

The price of tutoring rose when demand outran supply. Inflation is the same thing across the whole economy at once: people trying to buy more than the economy can produce, or the economy suddenly able to produce less.

• Capacity: the most the economy can produce with the workers, machines and materials it has right now.
• Demand-pull inflation: prices rise because total spending grows faster than capacity.
• Cost-push inflation: prices rise because producing things got more expensive, often from a supply shock like an oil cutoff.
• Money supply: how much money exists: cash plus the deposits banks create when they lend.
• Inflation expectations: how much inflation people think is coming.
• Wage-price spiral: rising prices lead workers to demand higher pay, which raises costs, which raises prices again.

Demand outruns capacity. Sam’s town can teach about 120 students, since that’s how many tutors and classrooms exist. Then every family gets a $2,000 government check and starts spending more on everything, tutoring included.

This is the most important idea here: extra spending turns into more output when there’s slack, and into inflation when there isn’t. The same check can be harmless in a recession and inflationary in a boom.

Costs jump. Rents in town double, and electricity rises because of an oil shock. Every center’s costs go up at once, so they all raise prices, and some close, so fewer students get taught. Prices up, output down.

Too much money. If everyone suddenly had twice as much money and nothing else changed, prices would roughly double. More generally, if money grows much faster than the stuff the economy produces, the extra money mostly raises prices: “too much money chasing too few goods.” It’s really the first cause seen from the money side, since new money gets spent. Fast money growth can come from banks lending heavily, or from a central bank creating money to pay for government spending.

Expectations. Suppose everyone in town starts expecting 5% inflation next year:

1. Leo asks Sam for a 5% raise, so his pay keeps up.
2. Sam raises her fees 5% to cover his raise and her rising costs.
3. Parents see prices rising 5%, so they ask their own employers for 5% raises.
4. Those employers raise their prices to cover the raises.

Inflation of 5% happens because everyone expected it. Once that loop gets going, it’s a wage-price spiral, and it’s very hard to stop. That’s why the Fed cares so much about credibility: if people trust it to keep inflation near 2%, they don’t build in 5%, and the loop never starts.

Real inflation usually mixes several causes, which is why economists argue about every episode.

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Who Wins and Who Loses

• Real wage: your pay adjusted for inflation, meaning how much it actually buys.
• Fixed payment: an amount set in dollars that doesn’t change with prices: a fixed-rate loan, a bond’s interest payments, many pensions.
• Indexed: automatically adjusted for inflation. US Social Security payments rise with the CPI, for example.
• Expected and unexpected inflation: what people planned for, and the surprise on top.

Expected inflation does little harm, because people build it into rates, wages and prices ahead of time. It’s unexpected inflation that shifts wealth around. Say everyone expected 2% inflation this year, and it came in at 6%.

Sam, the borrower. Her $5,000 loan charges a fixed 8%. She and the bank both expected 2% inflation, so they thought of it as roughly 6% in “real” terms: the bank gets back about 6% more buying power than it lent. With 6% inflation, the real rate is only about 2%. Sam repays in dollars that buy less than the ones she borrowed. Sam wins, the bank loses.

Leo, the worker. He got a 3% raise, which seemed fine when inflation was expected at 2%. With prices up 6%, his pay buys about 3% less than last year. Leo loses, at least until his next raise catches up, which often takes a year or more.

A saver with cash. $10,000 sits in an account paying 1%. After a year it’s $10,100, but things cost 6% more, so it buys about what $9,500 did a year ago. She lost about $500 of buying power without spending anything. That’s the inflation tax on holding cash.

A homeowner with a fixed mortgage. Someone locked in a 30-year mortgage at 3%. Inflation pushes up their wages and their house’s price, but the payment stays the same, so each year it’s a smaller share of their income. Big win. Many Americans who locked in very low rates around 2020 and 2021 were in exactly this position when inflation hit.

A retiree. One with a fixed private pension loses: the same check buys less every year. One living on Social Security is protected, since it’s indexed.

The government. It’s the biggest borrower of all, and inflation shrinks the real value of what it owes. That’s one reason people worry governments might be tempted to tolerate inflation.

The pattern: inflation moves wealth from lenders and savers to borrowers. It often hits poorer households hardest. They spend a bigger share of income on food, energy and rent, which tend to rise fast, and hold more of their savings in cash rather than in homes or stocks that keep up.

There’s also a cost nobody wins from: uncertainty. When nobody knows what prices will be next year, it’s harder to sign contracts, plan investments or set wages, and people spend energy protecting themselves instead of producing things.

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Why the Fed Aims for 2%, Not Zero

If inflation hurts, why not aim for zero? Because falling prices turn out to be more dangerous, and a little inflation gives the economy room to adjust.

• Deflationary spiral: falling prices causing less spending, which causes prices to fall further.
• Zero lower bound: central banks can’t cut interest rates much below zero, because people would just hold cash instead.
• Sticky wages: employers almost never cut people’s pay in dollars, even when business is bad.

Suppose prices across the economy start falling 3% a year.

Families wait. If tutoring will be cheaper next year, some families postpone signing up. Sam has less demand now, so she cuts prices further, which makes waiting even more sensible. The same logic hits cars, houses and business equipment, and the whole economy slows.

Sam’s debt gets heavier. Her loan payments are fixed in dollars, but her fees are falling, so each year repaying takes a bigger share of what she earns. In a deflation, borrowers lose and lenders win. If enough borrowers can’t pay, banks take losses and lend less. Since banks create money when they lend, less lending means less money, less spending, and prices fall further. This is debt deflation, and it’s a big part of why the Great Depression was so severe: US prices fell by roughly a quarter from 1929 to 1933.

The Fed runs out of room. To fight a slump, the Fed cuts rates, but it can’t go much below zero. With rates at 0% and prices falling 3%, borrowing still costs 3% in real terms, right when the economy needs it to be cheap.

Sticky wages, worked through. After an AI tutor arrives, demand for human tutors falls, and tutors’ pay needs to come down about 5% in real terms, from Leo’s $600 a month to the equivalent of about $570.

The real outcome is identical. But almost nobody accepts a smaller number on their paycheck. It feels unfair and hurts morale, so employers avoid it and often lay people off instead. With a little inflation, real pay can adjust quietly, and fewer people lose their jobs.

The 2% number isn’t a law of nature. New Zealand’s central bank adopted the first formal inflation target around 1990, most rich countries settled on about 2%, and the Fed made 2% its official goal in 2012.

Good falling prices and bad deflation. TVs, computers and solar panels have gotten far cheaper for decades because we got better at making them. That’s productivity, and it makes people richer: same money, more stuff. What’s dangerous is the whole price level falling because people aren’t spending, and that loop feeding on itself. Japan lived with mild deflation and weak growth for much of the late 1990s and 2000s, which is a big reason central banks fear it.

That distinction will matter for AI. If AI makes certain services much cheaper to produce, that’s the good kind, like TVs. The question is whether it stays limited to those services or hits wages and spending broadly enough to become the bad kind.

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When It Spirals: Hyperinflation

• Hyperinflation: prices rising extremely fast. A common definition is more than 50% a month.
• Monetizing the deficit: a government spends more than it collects in taxes, can’t borrow the difference, so its central bank creates new money to pay for it.
• Flight from the currency: people trying to get rid of their money as fast as possible.
• Dollarization: a country giving up its own currency and using someone else’s, usually the US dollar.

Say the town’s government can’t cover its spending. Taxes fall short, nobody will lend to it, so it pays its bills with newly printed money.

1. More money, same stuff. Prices rise, say 10% this month.
2. Taxes arrive late. They’re collected on last month’s income, so by the time they come in, they buy 10% less. The gap grows, so the government prints more.
3. People stop holding money. Once everyone expects prices to keep rising, holding cash means losing value every day. Leo spends his pay the moment he gets it. Families pay for tutoring months in advance. Money changes hands faster, pushing prices up further.
4. Contracts break. Sam stops charging in local money and asks for dollars, or groceries. Leo insists on being paid daily, then twice a day.

Each step feeds the next: the expectations loop with no brake on it. At 50% a month, compounding is brutal:

Hyperinflation isn’t ordinary inflation turned up a bit. It’s a collapse of trust in the money itself. Modern money is worth something only because people expect others to accept it tomorrow. It’s also why most countries make their central banks independent: if politicians can order money printed to pay their bills, the temptation is always there.

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A Real Case: 2021 to 2023

The inflation after the pandemic had all four causes at once.

Demand. In 2020 and 2021 the US government spent about $5 trillion on pandemic relief, including checks sent straight to households. Unlike QE after 2008, this money went to people who spent it.

Supply. Factories shut, ports jammed and chips ran short. Stuck at home, people bought furniture, electronics and cars instead of travel and restaurants, and supply chains couldn’t keep up. Then Russia invaded Ukraine in February 2022, and energy and food prices jumped.

Money. The Fed cut rates to zero and restarted QE on a huge scale. The money supply grew about 25% in 2020 alone.

Expectations. Through 2021, the Fed called the price rises “transitory,” expecting them to fade as supply chains healed. As they kept going, workers pushed for bigger raises and businesses raised prices more readily.

US inflation peaked at 9.1% in June 2022, the highest in four decades. The Fed then raised its rate from near zero to 5.25 to 5.5% by July 2023, the fastest increase since Volcker. Rising rates did what they always do to bonds: they lost value. Silicon Valley Bank had put depositors’ money into long-term bonds, and when their value dropped and depositors pulled out in a panic over a couple of days, it failed in March 2023.

Unlike under Volcker, inflation came down without a recession. Unemployment stayed low through 2022 and 2023. Economists call that a soft landing. Inflation fell to around 3% by mid-2023, but it has stayed above the 2% target since, and new tariffs have added to prices.

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What’s Next

Inflation is the price level rising, measured with a weighted basket. It comes from spending outrunning capacity, costs jumping, money growing too fast, and expectations that make themselves true. Unexpected inflation moves wealth from lenders and savers to borrowers. Central banks aim for about 2% rather than zero because deflation is more dangerous and a little inflation gives wages and interest rates room to adjust. Hyperinflation is a different thing: a collapse of trust in money when a government prints to pay its bills.

Pulling five parts together: economics is how people use limited resources to produce what others value. Output comes from labor and capital, multiplied by productivity. Prices, set by supply and demand, coordinate who makes and gets what. Money and credit move resources across people and time, with interest as the price of time. What anything is worth is its future benefits discounted to today, so prices run on expectations, while the real economy decides in the end whether those expectations were right. And who captures the value depends on bargaining power, not just on who creates it.

That can sound like a description of capitalism. Part 6 sorts out which parts every economy shares and which parts are where capitalism and socialism actually disagree, starting from what it means to own a business.