Chief executive officers of U.S. companies got a 12.1 percent pay raise in 2014, mainly driven by increases in the value of pension benefits, an analysis showed on Thursday.

Towers Watson & Co, a risk and HR management services provider, said the increase in CEOs’ median total pay was much greater than the 1.6 percent increase in 2013, as lower interest rates and other factors drove up pension value.

If the change in pension values were excluded from the analysis, CEOs’ total compensation would have increased 8.1 percent.

The data comes at a time when Democratic presidential candidate Hillary Clinton, under pressure from her party’s left wing to campaign against income inequality, voiced concern about the hefty paychecks of some corporate executives.

The analysis, based on 500 companies on the S&P 1500, that filed proxies disclosing 2014 pay by late March, said that 62 percent of companies paid annual incentive awards to CEOs that were above target levels, compared with 53 percent in 2013.

“The fact that CEO pay accelerated in a year when revenue growth, earnings and shareholder returns shined demonstrates that CEOs are being rewarded for performance,” said Todd Lippincott, North America leader of executive compensation at Towers Watson.

Target long-term incentives, the biggest component of executive pay in major companies, rose 7.1 percent in 2014, up from an increase of 5.9 percent in 2013, the analysis showed.

Advisory firm ISS on Tuesday estimated that U.S. CEOs’ median compensation rose nearly 13 percent in 2014.