This is general information, not financial advice.

When the headlines say inflation is 4.2% and the Fed says it's 4.1%, they aren't contradicting each other — they're using two different rulers. Here's the difference.

The two gauges

CPI — the Consumer Price Index, from the Bureau of Labor Statistics — is the headline number you see in the news. It tracks the prices of a fixed "basket" of goods and services that urban households buy, from groceries to rent to gasoline. Social Security raises, many wage contracts and tax-bracket adjustments are tied to it.

PCE — the Personal Consumption Expenditures price index, from the Bureau of Economic Analysis — is broader, and it's the gauge the Federal Reserve targets (at 2%). The Fed has preferred it since around 2000 and formally set a 2% PCE goal in 2012, as the San Francisco Fed explains.

Why they differ

Three things drive the gap.

1. Scope — what's counted. CPI measures only what households pay out of pocket. PCE also counts spending made on your behalf — most importantly, healthcare paid by employers, Medicare and Medicaid. So healthcare gets a much bigger weight in PCE (17%) than in CPI (7%), while shelter (rent and homeownership costs) looms larger in CPI (32%) than PCE (15%).

2. Substitution — how shoppers adapt. When one item gets pricier, people switch to a cheaper substitute (steak gets dear, you buy chicken). PCE updates its basket more often and captures that switch faster; CPI's more fixed basket is slower to adjust. This is the main reason PCE tends to run a bit lower than CPI.

3. Formula. The two use different math to combine prices, adding a smaller wedge.

Add it up and, since 2000, CPI has averaged roughly 0.4 percentage points higher than PCE. That's why May's data showed CPI at 4.2% but PCE at 4.1%.

Core vs. headline

Both gauges come in two flavors. Headline includes everything. Core strips out volatile food and energy, whose prices swing with weather and oil markets. Economists watch core to see the underlying, stickier trend — the part of inflation monetary policy can actually steer. That's why, when oil spikes, headline jumps but core moves less: in May, headline PCE hit 4.1% while core was 3.4%.

Which number should you watch?

Both — for different reasons:

  • Your paycheck and benefits are usually indexed to CPI. Cost-of-living raises and Social Security increases follow it.
  • The Fed's rate decisions track PCE against its 2% target. When you're trying to guess the Fed's next move, PCE is the number that matters.
  • Mind the gap. Because CPI runs higher, a moment when the Fed declares inflation "near target" on PCE can still feel painful to workers whose raises are pegged to the hotter CPI.

Neither gauge is "more real" — they answer slightly different questions about how prices are changing. Knowing which is which is the difference between reading an inflation headline and understanding it. Both are published free by the BLS (CPI) and BEA (PCE) every month.