Inflation

Inflation describes the overall price level, not any one price. As the Federal Reserve puts it, a jump in the cost of one product, or even several, is not inflation; a general increase across the economy’s goods and services is.

The figure most people hear comes from the monthly Consumer Price Index report from the Bureau of Labor Statistics. In the 12 months ending August 2026, the CPI for all urban consumers, the headline number, rose 3.4%. Core CPI, which leaves out volatile food and energy prices, rose 2.4%. Core figures show the trend; the headline figure is closer to what households actually pay.

The Federal Reserve targets a different gauge: 2% a year on the price index for personal consumption expenditures (PCE), a goal it reaffirmed in January 2026. A broad fall in prices is the opposite, Deflation; a slowdown in the pace of increases is disinflation.

A one-off jump, such as a poor harvest lifting the price of one crop, fades on its own. Inflation persists when price pressure is broad and people start to build higher prices into their plans. Economists usually point to four forces, which often act together. Over the longer run, the Federal Open Market Committee says inflation is primarily determined by monetary policy, which is why the Fed sets an explicit goal and raises or cuts interest rates to pursue it.

A few percent a year sounds small, but it compounds. By the Rule of 72, prices double in about 24 years at 3% inflation and about 36 years at 2%, so someone retiring at 62 can expect today’s grocery bill to roughly double by their mid-80s.

That is why planners separate nominal figures, the dollars printed on statements, from real figures that take inflation out. A 6% return in a year of 3% inflation is only about a 2.9% real return. Cash left for years in a low-rate account loses purchasing power even though its balance never falls.

The 4% rule raises each year’s withdrawal by the prior year’s inflation, so a burst of high inflation early in retirement lifts every later withdrawal, not just one year’s. Inflation also magnifies longevity risk: every extra year of life is another year for prices to compound.

Some parts of your finances adjust for inflation automatically. Social Security pays a yearly cost-of-living adjustment, 2.8% for benefits paid from January 2026. Federal tax brackets and the standard deduction rise with the chained CPI, and the 401(k) deferral limit went from $23,500 in 2025 to $24,500 for 2026. Treasury TIPS and I bonds tie their principal or interest rate to the CPI-U.

Other figures are fixed in dollars, so rising prices quietly erode them. The income thresholds for taxing Social Security benefits have never been indexed, and neither have those for the Net Investment Income Tax or the Additional Medicare Tax. As incomes rise with prices, more households cross these lines without any real gain. Many pensions and level annuities pay the same dollars for life, and a fixed-rate mortgage payment never changes.

No asset protects perfectly against inflation in every year, so plans usually combine several tools. Growth assets such as stocks have the potential to outpace inflation over long periods but can fall sharply in the short run. Inflation-linked Treasuries adjust with the CPI but can still lose market value when real interest rates rise. Income with a cost-of-living adjustment, above all Social Security, covers part of the risk that fixed income would otherwise leave you holding.

The assumption matters as much as the assets. State spending goals at today’s prices, pick a long-run inflation rate, then rerun the plan at a higher one. A plan that works at 3% and breaks at 4% is telling you how much margin it really has.

Most inflation errors in a long-range plan come from mixing dollars of different years, or from assuming an income keeps pace with prices without checking. The headline rate is also an average across urban households, so your own costs may rise faster or slower. None of these slips stops a spreadsheet from balancing; they surface decades later as a budget that no longer buys the same life. The most common: