The growth of women in the workforce is placing downward pressure on the amount of pre-retirement income that Social Security replaces.

A study by the Center for Retirement Research at Boston College examined replacement rates for the average worker and determined that a more accurate measurement of replacement rates is needed to target couples because they operate as a unit.

What the center found is that the amount of pre-retirement income replaced by Social Security depends on the labor force activity of both spouses. At the high end, couples with a non-working spouse get the replacement rate from the worker's benefit and from a spousal benefit, which could replace about 60 percent of the couple's pre-retirement income.