An insurer says it believes fixed annuities can help improve an investor’s overall returns even during years when investments perform well.

Income strategies specialists at Massachusetts Mutual Life Insurance Company, Springfield, Mass., come to that conclusion in a summary of results from comparisons of various relatively conservative asset allocations within a hypothetical retirement account.

The MassMutual analysts used an investment period that stretched from Jan. 1, 1980 to Dec. 31, 2006,

Although stocks did well over that period, portfolios that included fixed annuities could have done better, MassMutual analysts report.

The analysts compared one hypothetical account, in which $50,000 was invested in stocks and $50,000 in bonds, with a portfolio in which 33.3% of the $100,000 was invested in stocks, 33.3% in bonds, and 33.3% in a life-only fixed annuity.

The investor who bought the fixed annuity would have ended up with almost $670,000 by the end of 2006, while the investors who stuck with stocks and bonds would have had only about $490,000, the MassMutual analysts write.