I have been of the belief that Social Security benefits are determined by taking the average income of all the years of employment.

Q. I have been of the belief that Social Security benefits are determined by taking the average income of all the years of employment. I recently heard that it is the average of the highest thirty-five years of employment. Which is correct?

A. Monthly Social Security benefits are determined on average monthly earnings over 35 years. When a benefit application is filed, the Social Security Administration indexes lifetime earnings to bring them up to date. The highest 35 years of earnings are selected and averaged to determine the monthly benefit. If a worker has more than 35 years of earnings, excess lower-earning years are disregarded. If the worker has fewer than 35 years of earnings, some zero income years are included in the calculation.