The goal of any retirement mutual fund manager is to provide a well-balanced portfolio of stocks, bonds and cash. However, no two retirement mutual funds are alike, with some funds seeking to build a steady stream of income for people currently in retirement and other funds whose objective is to build portfolios for people who are 30 or 40 years away from retirement.

The approach fund managers take to meet the retirement goals of specific individuals is through asset allocation, and the underlying basket of assets that make up any retirement mutual funds are never the same. Therefore, investors seeking to build steady streams of income during retirement through mutual funds must know some of the top-rated retirement funds and which assets the managers invest in to achieve that income.

Top-Rated Target Retirement Income Mutual Funds

• Vanguard Target Retirement Income Fund- The goal of this mutual fund is to provide an investor with a steady stream of monthly income during retirement. The fund holds large-cap stocks and high-quality bonds. Over the next 12 months, the fund managers plan to add one broad international stock index fund to gain higher exposure to international equities. As of 2015, the fund holds $11.6 billion in assets and returned a 5.35 percent yield over the past five years.

• Fidelity Freedom Index Income Fund- This retirement mutual fund seeks high current income for investors along with capital appreciation. Fund managers combine stable domestic equity funds, high-value bond funds and international funds from emerging or developed markets. Over the past five years, the fund returned a 4.40 percent yield to its investors.

Top-Rated Target-Date Retirement Mutual Funds

• AB 2020 Retirement Strategy- This retirement mutual fund seeks higher than average total returns on a consistent basis by investing in the AllianceBernstein Pooling Portfolios. As the target retirement date approaches, fund managers will seek more conservative assets until the investors 15th year of retirement. Over the past five years, the fund returned a 9.3 percent yield to its investors.

• BlackRock LifePath 2020 Portfolio- The goal of this fund is to build retirement income through quantitative measured risk. The BlackRock LifePath fund managers invest all of their capital assets in a separate mutual fund called the 2020 Master Portfolio, which invests in money-market mutual funds, equities and bonds. Over the past five years, the fund returned an 8.3 percent yield to its investors. According to U.S. News and World Report, the fund is a below average risk compared to other funds in the same classification.

• BMO Target Retirement 2020 Fund- This retirement mutual fund seeks to build growth and income by investing in a basket of affiliated BMO mutual funds. The BMO Target Retirement Fund cannot hold more than 80 percent of its assets in other funds that invest specifically in stocks. Over the past five years, the fund returned an 11.1 percent yield to its investors.

The U.S. News and World Report Money rated the top target retirement income mutual funds by polling 41 leading researchers and analyzing their ratings. In addition, the target-date retirement mutual funds use 2020 in the name of the fund as that is the target retirement year for its investors.