WASHINGTON — If you are wondering if it's still worth the worry to invest in a 401(k) or similar workplace retirement plan, stop your hand-wringing.

It is.

Or at least it's worth it for the people who consistently invest, according to new research by the Employee Benefit Research Institute and the Investment Company Institute.

Yes, it's been painfully apparent that 2008 was a crushing year for those of us who invest. The average 401(k) retirement account fell 24.3 percent, according to EBRI and ICI.

But retirement plan data studied by EBRI and ICI found that over a five-year period — from 2003 to 2008 — 401(k) participants saw their account balances increase at an average annual rate of 7.2 percent. The calculations include ongoing worker contributions, employer contributions, and investment gains and losses.

For all participants in the EBRI/ICI 401(k) database, the average account balance at year-end 2008 was $45,519, compared with $65,454 in 2007. If you need a benchmark for how bad that 30.5 percent decline was, consider that the Standard & Poor's 500 stock index declined 38.5 percent last year.

Take that kind of hit and it's enough to unnerve even a seasoned investor. So it's understandable that many people have been wondering of late whether they are foolishly investing the little bit of extra money they have now for the dream of having enough money to stop working at some point in their lives.

"Basically the engine of saving and investing that the 401(k) presents still works," said Sarah Holden, ICI senior director of retirement and investor research.

For retirement plan participants consistently investing, the average account balance rose to $86,513 at year-end 2008 from $61,106 at year-end 2003. Among the same group, the median account balance (or midpoint) increased to $43,700 at year-end 2008 from $25,507 at year-end 2003, an annual increase of 11.4 percent over the five-year period.

Holden said that even though retirement plan participants, like most investors, suffered one of the deepest bear markets in modern history in 2008, the growth in account balances — although modest — still shows that disciplined investing through workplace plans will help employees meet their retirement saving goals.

The EBRI/ICI study is worth keeping track of because it is based on 24 million participants, including 6 million who have had 401(k) accounts with the same employer each year from 2003 through 2008. The 2008 database covered 48 percent of active 401(k) plan participants, 12 percent of plans, and 47 percent of 401(k) plan assets. Information is gathered from participants in 401(k) plans of varying sizes — from very large corporations to small businesses — and with a variety of investment options.

In the latest findings, EBRI and ICI found that the bulk of 401(k) assets continued to be invested in stocks. At year's end in 2008, 56 percent of 401(k) participants' assets were invested in equity securities through equity funds, the equity portion of balanced funds, and company stock. At least investors are getting the word that they shouldn't be overexposed in their own company stock. The data found that the share of 401(k) accounts invested in company stock continued to shrink, falling by nearly 1 percentage point to 9.7 percent in 2008.

Forty-one percent of plan assets were in fixed-income securities, such as bond and money market funds.

Overall, what's the takeaway from this data?

And I'm not just asking for my financial health. It's important you ask yourself this question too when you read about these reports. If you don't, you'll continue to be scared or even worse, jump out of the market altogether.

"If there is a takeaway for plan participants, it's that even having had the worse equity market since 1931, if people stayed consistent they still end up doing fairly well," said Jack VanDerhei, EBRI director of research.

One thing this study does prove is that we still have to view retirement investing over the long haul. You can't look at one horrible investment year — in this case 2008 — and declare that investing is for chumps.

Michelle Singletary writes for the Washington Post. Her e-mail address is singletarym@washpost.com.