Replacement rates, which compare individuals' initial Social Security benefits with previous wages, are often used to determine whether or not recent retirees can maintain their preretirement standard of living. Replacement rates, however, can be unsteady measures. As discussed in a previous brief, they look different depending on the wage (for example, average, highest, or most recent) with which a new Social Security benefit is compared. But such rates can also appear different over the course of retirement.