By ELLEN E. SCHULTZ and TOM MCGINTY

Pensions for top executives rose an average of 19% in 2008, with more than 200 executives seeing pensions increase more than 50%, according to a Wall Street Journal analysis.

The executive-pension growth stemmed partly from generous pension formulas, which are based on executive pay, according to the filings. Also adding to the pension jumps are arcane techniques that have received little scrutiny, including increases triggered when an executive reaches a certain age or when companies change interest rates used to calculate the pensions.

Executive pensions rose even as the share prices at the companies declined an average of 37% in 2008 and many firms froze employee pensions and suspended retirement-plan contributions.

The growth of such supplemental executive retirement plans, or SERPs -- which can be worth tens of millions of dollars to executives -- largely has been overlooked amid a backlash against executive pay, particularly at banks and other companies receiving taxpayer bailouts.

Rules that became effective in 2007 have made more information available by requiring companies to report the estimated total value of each top executive's pension and the pension's growth over the prior year.

Using two years of improved disclosures compiled by research firm Capital IQ, the Journal examined 340 companies with pension plans in the Standard & Poor's 500-stock index and calculated the annual change of the value of the named officers" pensions. The analysis excluded executives who didn't participate in the plans in both 2007 and 2008.

Surging pay fueled much of the growth of executive pensions, which generally are calculated by multiplying pay by years on the job, a formula that can produce steep increases in pension values when either the pay or years of service increases.

Richard T. Clark, Merck & Co.'s chief executive, saw the portion of his compensation used to calculate his pension rise more than $6 million in 2008, which in turn helped boost the value of his pension to $21.7 million from $11.9 million.

ConocoPhillips included "certain incentive payments" in the compensation it used to calculate CEO Jim Mulva's pension, according to its filing. The additional compensation helped boost his pension $9.5 million, to $68.2 million.

Big bonuses, especially in the final years of executives' tenure, boosted some top executive pensions substantially, filings show. One of Exxon Mobil Corp.'s two supplemental pension plans for executives uses the three highest bonuses in the five years prior to retirement to calculate the executive's pension. Thanks to this, a $4 million bonus to CEO Rex Tillerson in 2008 helped push the total value of his pension to $31 million from $23 million.

An Exxon spokeswoman pointed out that the proxy states that "by limiting bonuses to those granted in the five years prior to retirement, there is a strong motivation for executives to continue to perform at a high level."

Merck and ConocoPhillips confirmed the information and had no further comment.

Awarding executives additional years of service, a practice that some pay watchdogs have criticized, remains common, filings show.

PG&E Corp. awarded CEO Peter Darbee an additional five years of service in 2008, which helped boost his pension to $5.2 million from $3.8 million, a 38% rise. A PG&E spokesman said Mr. Darbee's benefit was increased to "address disparity between his pension benefits and other officers" at PG&E.

In February 2008, Constellation Energy Group Inc. awarded Chairman and CEO Mayo Shattuck with an additional 2µ years of service, which helped increase his pension by $10.3 million, a 45% increase, according to company filings. A Constellation Energy spokesman said the compensation committee decided to count Mr. Shattuck's years as a director at the company, and said the increase in his pension is "due in large part to a performance bonus our CEO received after the company posted record results in 2007."

Reaching a milestone birthday also can enhance an executive's pension. Altria Group Inc. CEO Michael E. Szymanczyk's pension rose when he turned 60 last year, triggering a subsidy built into the pension formula, boosting its total value to $23.5 million.

Mr. Szymanczyk benefited from an early retirement subsidy, a feature widely used in employee pensions in the 1980s and 1990s. The subsidy, which typically kicks in when a worker reaches age 55 or 60, enables him to retire with the same pension benefit he would have received if he remained on the job until age 65. The subsidies were intended to encourage older workers to retire.

An Altria spokesman confirmed the information, and said Mr. Szymanczyk's total compensation was roughly flat in 2008.

Under the rules implemented in 2007, companies also must disclose the assumptions they use to value the benefits. Many companies reduced an interest rate they use to calculate the pension, which boosted the accumulated present value, according to filings. Reported in the proxy, this is the company's estimate of what all the monthly payments to the executive in retirement would be worth in today's dollars. The lower the interest rate, the higher the pension payout.

Goodyear Tire & Rubber Co. lowered the rate it uses to calculate lump sums paid out from its SERP to 4% from 5.25%, which accounted for $1.6 million of the $6.2 million increase in CEO Robert Keegan's pension. Its total value: $17.5 million. Goodyear froze salaried employees' pensions at the end of 2008, saying it "could impair our ability to achieve or sustain future profitability." Goodyear said it also froze one of its pension plans available to executives and highly paid employees. And it said the top executives could receive payouts larger or smaller than the amounts shown in the proxy if the assumptions used to calculate pensions change.

That is true. But the Journal's analysis showed that nearly all executives who departed their companies in 2007 and 2008 received pension payouts at least equal to the amount that was disclosed in the prior year's proxy.

Write to Ellen E. Schultz at ellen.schultz@wsj.com and Tom McGinty at tom.mcginty@wsj.com