There is a thriving cottage industry based on the observation of the behavior of retirement plan investors. Are they saving more or less after Wall Street's severe slide? Has the market's five-month rally prompted them to renounce their conservative ways and embrace stocks once again?

Truth be told, the subjects of this intense scrutiny were decidedly inert creatures before the economic convulsions and remained pretty much so throughout the storm. Nevertheless, significant subsets of the species were prone to questionable behavior prior to the calamity, an empirical observation that remains true today.

"High-level metrics of participant savings behavior were relatively unchanged in 2008, a positive development given the economic and market conditions," said Jean Young, a researcher for Vanguard.

Her conclusion was based on a study of more than 3 million retirement plan investors in more than 2,200 defined contribution plans administered by the Valley Forge-based mutual fund giant. The research detailed how the investors behaved last year. Behavioral changes since the market turned in March were not measured.

According to Vanguard's study, 73 percent of contributions went to stocks last year, "not a marked shift from 2007."

Participants who had balances in their retirement fund at the beginning and end of 2008 experienced a median decline of 14 percent last year. That was a much milder form of the malady than broad market indexes endured. More than a third said their balances rose or remained flat because of contributions, conservative investments, or both.

The percentage of their paycheck that investors devoted to their retirement plans fell slightly, from 7.3 percent to 7 percent.

Vanguard believes that's because more plans adopted automatic enrollment, which allows companies to place workers into 401(k) and deduct contributions -- generally about 3 percent -- from their paychecks. Workers can ask to get out, but given the initiative that requires, many remain in the plan.

"Participants in general are very passive. Once they get into the plan, they generally stay in there in whatever percentage they're investing," said Sandra Pappa of Buck Consultants, Downtown.

As for irregular behavior, Vanguard found that a third of retirement investors had extreme positions in stocks. That is, they either entrusted all of their savings to stocks or less than 20 percent.

T. Rowe Price Associates also reports that retirement investors are, for the most part, doing the same types of things. Participants are contributing an average of 7.5 percent of their pay. That's down from 8 percent going into last fall.

"We think that is mainly due to the adoption of automatic enrollment," said spokesman Robert Benjamin. "We've seen a real commitment among our investors to not making changes."

Of late, the Baltimore investment company's call centers report a renewed interest in stocks and less interest in bonds and stable value funds.

"That's another sign you could interpret as people calming down," Mr. Benjamin said.

Earlier this month, Fidelity Investments reported that the number of retirement investors who increased contributions to their accounts in the second quarter outnumbered those who decreased contributions. That reversed a trend in the previous three quarters.

The Boston investment firm's study was based on behavior of 11.2 million participants in more than 17,500 retirement plans.

The data also revealed that 68 percent of contributions made in the first half went to stocks. Equity allocations had hovered around 75 percent in recent years after topping out at more than 80 percent in 2000, Fidelity said.

As for stupid 401(k) tricks, Fidelity found that among workers 50 and older, 11 percent hold no stocks in their retirement accounts and 14 percent have nothing but stock in their accounts.

Ms. Pappa said inertia served most retirement investors well during the recent market turmoil. But it can hurt them as well.

A case in point, she said, are retirement investors who, after realizing gains from their stock investments in the years leading up to the market decline, did not allocate a portion of those gains to bonds and other investments to keep their portfolio balanced.

"When you talk to really astute investors, they were really worried back in mid-2008, and they took action and moved money to cash," Ms. Pappa said.

Whether Wall Street's stumble will change the long-term behavior of retirement savers remains to be seen.

New jobless claims rose unexpectedly last week, and many economists believe that the unemployment rate, currently at 9.4 percent, will rise in coming months.

The fear of losing their jobs could cause workers who remain employed to reduce their contributions or change their investment strategy. Those who are thrown out of work could tap retirement savings to make ends meet.

Rest assured. Researchers analyzing these generally inert creatures will keep us abreast of the latest developments in this burgeoning field of behavioral science.