Fixed-income annuities increase long-term retirement wealth, according to a study by MassMutual Financial Group. The study back-tested the performance of various asset allocations within a hypothetical $100,000 retirement account for the period from Jan. 1, 1980, to Dec. 31, 2006. Account A, evenly divided between U.S. equities and U.S. bonds, ended with $489,346. In account B, 33.3% of the $50,000 bond allocation comprised a life-only fixed-income annuity, and that account ended with $667,688. In account C, bonds comprised 30% with 20% was a life-only fixed-income annuity, and that account ended with $735,292.