If you wonder how such a large gap could develop, the proximate, or most immediate, factor involves the way in which CEOs now are able to rig things so that the board of directors, which they help select -- and which includes some fellow CEOs on whose boards they sit -- gives them the pay they want. The trick is in hiring outside experts, called "compensation consultants," who give the process a thin veneer of economic respectability.
The process has been explained in detail by a retired CEO of DuPont, Edgar S. Woolard, Jr., who is now chair of the New York Stock Exchange's executive compensation committee. His experience suggests that he knows whereof he speaks, and he speaks because he's concerned that corporate leaders are losing respect in the public mind. He says that the business page chatter about CEO salaries being set by the competition for their services in the executive labor market is "bull." As to the claim that CEOs deserve ever higher salaries because they "create wealth," he describes that rationale as a "joke," says the New York Times (Morgenson, 2005, Section 3, p. 1).
Here's how it works, according to Woolard:
The compensation committee [of the board of directors] talks to an outside consultant who has surveys you could drive a truck through and pay anything you want to pay, to be perfectly honest. The outside consultant talks to the human resources vice president, who talks to the CEO. The CEO says what he'd like to receive. It gets to the human resources person who tells the outside consultant. And it pretty well works out that the CEO gets what he's implied he thinks he deserves, so he will be respected by his peers. (Morgenson, 2005.)
The board of directors buys into what the CEO asks for because the outside consultant is an "expert" on such matters. Furthermore, handing out only modest salary increases might give the wrong impression about how highly the board values the CEO. And if someone on the board should object, there are the three or four CEOs from other companies who will make sure it happens. It is a process with a built-in escalator.