Equity-Indexed Annuities combine a guaranteed minimum interest rate, with a potential for greater growth linked to a specific equities market index such as the Standard & Poor's 500 index. If the chosen index rises sufficiently during a specific period, a greater interest rate is credited to the contract owner's account for that period. This type of annuity can also be purchased with a single lump sum of cash, with installment payments over time, or with flexible payments.