Annuity expressed in terms of benefit units instead of fixed dollar amounts. Annuity in which the amount of each periodic payment fluctuates according to some variable factor. Under an equity annuity plan, payments vary according to the value of a specific portfolio of common stocks and similar investments. Under a cost-of-living plan, benefits are adjusted to reflect variations in a specific index, such as the Consumer Price Index of the Bureau of Labor Statistics. An insured variable` annuity is one under which the benefit varies according to the investment results of an insurance company's separate account.