Every year, firms dutifully detail what their five highest paid executives receive in compensation. The reported pay is used as a benchmark by other firms, and is oft-quoted by the press to highlight which CEO got the biggest paycheck. But the reported numbers do not always reflect reality, which in the compensation world is referred to as realizable pay.

In a study published Thursday, the compensation advisory firm Equilar looked at the realizable pay over a three year period for a group of S&P 1500 CEOS.