The investment industry is great at making the complex seem simple.

Take target date funds, those 401(k) menu choices with names like Target 2020 or Retirement 2040. The names imply you can pick a retirement date, select the fund and watch the money pile up until you’re ready to clock out for good. The fund managers handle the asset allocation — which presumably grows safer as retirement nears.

The great bear market of 2008 exposed that fantasy. Even funds with a target date of 2010 — intended for workers who were nearly out the door when the stock market plunged — lost an average of 23 percent of their value in 2008.

The plunge prompted a round of soul-searching for the investment industry, with some hard-hit funds deciding to scale back risk in older workers’ portfolios. Some managers have also cut fees to make target date funds more appealing.

And workers, despite their searing bear market experience, haven’t lost faith in target date funds. Morningstar says the funds took in $47.5 billion last year, swelling their assets to $341 billion.

Historically, investors’ faith in the simple concept has been rewarded. The stock market, as measured by the Standard & Poor’s 500 index, remains 18 percent below its October 2007 record level. But target date funds as a group are up 5 percent since then, according to a report Morningstar published this spring.

The funds invest in stocks, bonds and sometimes other investments. They reduce their stock holdings as the retirement date nears, but that’s where things get complicated. The glide path — the route from an aggressive young person’s portfolio to a safer one compatible with retirement — differs greatly from fund to fund.

The 2010 funds— aimed at people who are already retired — have stock allocations ranging from 20 percent to 67 percent. The funds at the high end figure that folks will live 30 years or more in retirement, so they need their assets to keep growing. The 20-percenters figure that once you stop working, you ought to take less risk.

Neither philosophy is wrong, but you need to read the fund documents to find out which path your fund is taking. And there’s no reason why you can’t pick, say, a more conservative 2020 fund, even though you plan to work until 2030.

The fund itself is very rigid as far as its rules, says Rick Hill, principal at Hill Investment Group in Clayton. If you think the allocation is too conservative or too aggressive, then pick a different dated fund that fits your needs.

Many investors who were shocked by their target-date losses in 2008 probably had never read their fund’s prospectus. The Labor Department has proposed new disclosure rules that would make the reading easier, including a graphic illustration to show how each target fund’s glide path works.

At the same time, the Securities and Exchange Commission is talking about lengthening the funds’ names. Instead of just Target 2020, a fund might have to call itself Asset Allocation 2020 40-60, signifying that in its target year, the fund would hold 40 percent stocks and 60 percent bonds.

Experts are divided on whether a name change would provide valuable information or merely confuse investors. Most advisers agree, however, that this class of funds has improved over the past couple of years.

As the product developed, the warts came forth, and there was more scrutiny and questions, says Patrick Shelton, managing member of Benefit Plans Plus in Creve Coeur. But then the funds got stronger and stronger. They’re here to stay.

Sean Duggan, a 401(k) consultant at Moneta Group in Clayton, is a fan of target date funds, mainly because he likes the way investors use them.

For one thing, he said, too many workers take a buy-it-and-forget-it approach to investing. A target date fund, sometimes called a life cycle fund, won’t let a 60-year-old worker carry on blithely with the all-stock approach she chose at age 30.

A sizable group of workers does just the opposite, aggressively managing their money in response to market changes. Trouble is, they usually panic and sell when the market is down, or get euphoric and buy more stocks at a market peak.

Target date investors don’t usually make those mistakes, Duggan says. When we had 2008 happen, we talked to our clients and their participants, and we didn’t have any people in life cycle funds calling and saying, ‘Get me out.’

It may be a psychological difference: They know a professional manager chose the asset allocation, so they’re less likely to feel like they made a mistake, and they’re more likely to stay the course.

Americans in general are woefully unprepared for retirement, and woefully undereducated about investments. They really are hungry, though, for a simple way to overcome those deficits.

For all its flaws and hidden complexities, the target date fund may be their best bet.