Unlike boards the UK, recent hiring and exit packages for top executives at Morgan Stanley and Boeing suggest that boards in the U.S. don't fear shareholder revolts against towering executive pay packages.
According to the Chicago Tribune:
When it comes to explaining the non-stop escalation in CEO pay, compensation experts point to several phenomena: the rise of the compensation consultant, the power of the comparison group and the role of the single candidate.…. When a compensation consultant wants to bolster a CEO's argument that he should be receiving more, he carefully selects a group of other CEOs that will be used for comparison.