BOSTON (

TheStreet

) -- Companies that have shifted employees to 401(k) accounts from pension plans don't necessarily gain much, according to international consulting firm Watson Wyatt.

A review of 82 publicly traded companies that froze or closed their pension plans between 2003 and 2007 found there was an insignificant or negative effect on their stock prices. Contrary to previous research and assumptions, Watson Wyatt said that in 71 of 82 cases, companies' share prices didn't change much in the 23 days around an announcement of retirement-plan changes.

"Freezing a plan may produce some accounting gains, but it will not provide companies with long-term cash-flow relief -- either on an absolute level or volatility -- for many years," says Mark Warshawsky, director of retirement research at Watson Wyatt. "Also, even if these freezes do lead to savings, there will be no immediate positive effect on firm value. It could even become diminished in the long run if employees begin to view the firm as an uncompetitive employer in light of its shrinking commitment to retirement and its transfer of risk to employees."

In an analysis of pension plans released late last month, the firm found that 190 members of the 2009 Fortune 1000 list have frozen defined-benefit-pension plans, compared with 169 companies last year and only 45 six years ago.

Industries with higher defined-benefit-plan sponsorship rates, such as utilities and manufacturing, are less likely to freeze a plan. An opposite trend holds true. Almost half of the direct-benefit-plan sponsors in the financial-services industry and a third in the automobile industry have frozen plans.

Freezes can take various forms. Traditional pensions, whose formula relates to pay and years of service, can halt the years-of-service component, disregard future salary increases or both. In a closed plan, current employees continue to earn pension benefits, but employees hired after a fixed date can't participate in the plan.

Among the companies that have a pension freeze in effect are

Cigna

(CI) - Get Report

,

Wells Fargo

(WFC) - Get Report

,

Anheuser-Busch

(BUD) - Get Report

and

Kimberly-Clark

(KMB) - Get Report

.

The percentage of companies in the Fortune 1000 sponsoring an active pension has decreased significantly over the past six years. In 2004, 59% of companies maintained a defined-benefit plan that wasn't frozen, compared with 42% in 2009. Over those six years, the number of Fortune 1000 firms that sponsored one or more frozen plans more than quadrupled, from 45 in 2004 to 190 in 2009. In 2004, only 7% of sponsors had a frozen pension. In 2009, 31% maintain a frozen pension plan.

Though scaling back, freezing or eliminating direct-benefit plans may seem to be a financial necessity, the benefits may be overstated.

"This strategy could come with substantial hidden costs for employers, who could face increased difficulties in managing the retirement of their workforces, and for employees, who could face reduced retirement resources as a result of a frozen pension plan or a reduced 401(k) match," says Alan Glickstein, a senior retirement consultant at Watson Wyatt.

-- Reported by Joe Mont in Boston. Feedback can be sent to joseph.mont@thestreet.com.