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

Towers Watson, a risk and HR management services provider, said the increase in chief executives' median total pay was much greater than the 1.6 per cent 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, chief executives’ total compensation would have increased 8.1 per cent.

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 per cent of companies paid annual incentive awards to chief executives’ that were above target levels, compared with 53 per cent in 2013.

"The fact that chief executives' 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 per cent in 2014, up from an increase of 5.9 per cent in 2013, the analysis showed.

Advisory firm ISS on Tuesday estimated that US chief executives' median compensation rose nearly 13 per cent in 2014.

Reuters