Exxon Mobil Corp. (XOM) Chairman and Chief Executive Rex Tillerson's total compensation declined 30% to $28.1 million in 2013, as the previous year included a hefty benefit from a change in pension value.

Mr. Tillerson received about $2.7 million in base salary, $150,000 more than a year earlier, and cash bonuses totaling $3.7 million, down from about $4.6 million in 2012.

He also received stock awards valued at about $21.3 million, an 8.3% increase from 2012, according to the company's proxy filing.

Mr. Tillerson's compensation package for 2012 was propped up by more than $13 million due to a change in pension value and nonqualified deferred compensation earnings. In contrast, last year's change in pension value was negative, but SEC regulations don't allow for inclusion of negative pension amounts in the proxy summary compensation tables, the company said. Reflecting the pension change, his pay for 2013 was $21.9 million.

Other Exxon top executives saw their base salaries increase, with Senior Vice President Andrew Swiger receiving $1.1 million in 2013, up from $962,000 in 2012. Another senior vice president, Mark Albers, received a 7.1% increase in base salary to $1.1 million, while Senior Vice President Michael Dolan's base salary rose 9% to $1.2 million. And Stephen Pryor, Exxon vice president and president of ExxonMobil Chemical Co., received a 3.4% increase in base salary to $1 million.

The world's largest publicly traded oil company is also the largest natural gas producer in the U.S. since its $25 billion acquisition of XTO Energy Inc. in 2010. Exxon has added to its shale-gas assets through additional deals since then.

Exxon spent more money but pumped less oil and natural gas last year, leading to a 27% drop in profit for America's biggest energy producer, the company reported in January.