A life annuity is a financial contract in the form of an insurance product according to which a seller (issuer) — typically a financial institution such as a life insurance company — makes a series of future payments to a buyer (annuitant) in exchange for the immediate payment of a lump sum (single-payment annuity) or a series of regular payments (regular-payment annuity), prior to the onset of the annuity. The payment stream from the issuer to the annuitant has an unknown duration based principally upon the date of death of the annuitant...