The Thrift Savings Plan acted on Monday to have its automatic pilot investment funds steer a more aggressive course.

Following a consultant’s recommendation, the TSP will shift the investment mixes in its “lifecycle” funds, what it calls L Funds, more toward stocks. The goal is to “improve outcomes for existing L Fund participants while not unreasonably increasing risk levels,” according to a summary that the TSP staff presented to the program’s governing board.

The TSP, a 401(k)-like program for federal and military personnel and retirees, has nearly 5.3 million accounts totaling more than $577 billion. More than a third of TSP account holders have at least some of their money in lifecycle funds and 17 percent have all of their money in them—in total, more than $118 billion, a fifth of the total.

Lifecycle funds are designed to maintain ratios among types of investments in an account over time even as returns on those investments vary. They mix investments in stocks and bonds in proportions that vary according to when the account holder expects to begin withdrawals—the longer the holding date, the more they tilt toward stocks.

The TSP offers target date funds for 2020, 2030, 2040 and 2050 plus an “income” fund for those already taking withdrawals, or who are close to it. The money is invested in the TSP’s five core funds—one tracking an index of large U.S. companies, one of smaller U.S. companies, one of international stocks, one of the U.S. bond market and another of special-issue government securities. TSP investors may invest in any combination of the core funds and the lifecycle funds and may change their allocation at any time.

The income fund stays constant, with 20 percent spread across the three stock-based funds and the rest in the lower-risk government securities and bond funds. In contrast, the 2050 fund is more than 80 percent invested in stocks; it and the other target date funds have become more conservative as their projected withdrawal dates approach.

However, effective immediately, the percentages of stocks in the 2030, 2040 and 2050 funds will be frozen at their current levels. That will continue for a number of years until those percentages match the levels they would have reached had they started with a more aggressive profile of about a tenth more in stocks.

“We are pushing out the time frame where they become more conservative,” spokeswoman Kim Weaver said. “We thought that was the least shocking way to do it” in contrast to immediately boosting the share of stocks in those funds and thus increasing investors’ exposure to risk, she said.

The share of stocks in the 2020 fund also will decline more slowly although that will make only a small difference. That fund is only slightly more aggressive than the income fund and will have the same mix in two years, when they will merge.

Also, effective in January the TSP will increase from 30 to 35 percent the portion of each fund’s stock portfolio that is invested in the international stock fund. And starting in 2020, it will raise the stock allocation in the income fund from 20 to 30 percent, phased in over 10 years.

Those decisions were finalized Monday at the monthly meeting of the TSP’s governing board, which was not required to vote on the changes but could have acted to block them. They follow a report from the Aon Hewitt consulting firm concluding that the “participant demographics suggest it is reasonable” to increase the share of stocks in those portfolios.

One such factor is that participants are beginning their withdrawals later—rising on average from 61 to 63 in recent years—lengthening their investment periods. Also, the TSP is now able to more accurately project investors’ future annuity benefits, which the L fund allocations take into account, according to the staff report.

The study also concluded that overall the TSP’s lifecycle funds are more conservative and less weighted toward international stocks than similar funds offered by mutual fund companies and other retirement savings programs.