Average Indexed Monthly Earnings (AIME)

Average indexed monthly earnings is the earnings measure Social Security uses to start the retirement benefit calculation. The agency takes each year of a worker's covered wages, adjusts the earlier years upward so they are comparable to wages today, keeps the 35 highest of those adjusted years, adds them together, and divides by 420, the number of months in 35 years. The result is a single monthly figure, the AIME, which is then run through the bend-point formula to produce the primary insurance amount.

The indexing step is what makes the measure fair across a working life. A dollar earned in 1990 bought far more than a dollar earned today, so counting it at face value would understate what the worker actually contributed. Social Security corrects this by multiplying each past year's earnings by an indexing factor tied to the national average wage index. The indexing is frozen at the year the worker turns 60: earnings in the year they turn 60 and every year after are counted at their actual nominal value, not indexed. Only wages up to the Social Security taxable maximum in each year count, because only those wages were subject to the tax.

Two features of the 35-year rule matter in practice. First, it always uses 35 years, so a worker with only 30 years of earnings has five zeros averaged in, which pulls the AIME down. Continuing to work can replace a zero, or a low early year, with a higher one and raise the benefit even late in a career. Second, because the divisor is fixed at 420 months, a single very high year cannot dominate the average the way it might in a shorter window. The AIME is the reason Social Security rewards a long, steady earnings history rather than a few peak years.

The agency lists every year of covered earnings, indexes the years through age 59 to the national average wage index, selects the 35 highest indexed years, sums them, and divides by 420 months.

Hypothetical. Suppose a worker's 35 highest indexed years of earnings add up to $2,100,000. Dividing by 420 months gives an AIME of $5,000 a month. If that same worker had only 33 years of earnings, two zeros would be averaged in, the sum of the 35 counted years would be smaller, and the AIME, and therefore the eventual benefit, would come out lower. Replacing a zero year with a year earning $80,000 of indexed wages would add $80,000 to the numerator and raise the AIME by roughly $190 a month before the benefit formula is even applied.

Strengths of the measure

• Indexing past wages to wage growth keeps a 40-year career comparable across decades of inflation.
• Using 35 years rewards steady lifetime earnings rather than a few high years.

Where it works against people

• Fewer than 35 years of earnings forces zeros into the average, which can sharply reduce the benefit for people with interrupted careers.
• Only earnings up to the taxable maximum count each year, so very high earners see none of the wages above that cap reflected in their AIME.