They both work a 60-hour week. And neither says he is motivated by the money. But except for those two similarities, the INC. 100 CEOs and their counterparts at the heads of America's largest corporations are like distant relatives from the same family.

While little attention has been paid to charting the demographics of the CEOs of the Fortune 500, two academic studies looking at the CEOs of America's 800 largest corporations were recently published in Business Horizons magazine. The differences are more striking than the similarities.

The INC. 100 CEO is younger. The median age of those leading the academic 800 is 57, with 87% over 50, while the median age of the INC. 100is 48, with only 40% over 50. More than 4 out of 5 of the 800 come from upper-middle-class backgrounds, the children of professionals or corporate executives. The INC. 100 are more mainstream middle-class, half of them the offspring of entrepreneurs themselves. There is only one woman among the entire 800, Katharine Graham of Washington Post Co.; there are three women on the INC. 100: Lore Harp of Vector Graphic Inc., Elisabeth Claiborne Ortenberg of Liz Claiborne Inc., and Sandra Kurtzig of ASK Computer Systems Inc.

The most common background of the 800 was finance; the INC. CEOs consider finance their greatest weakness. The fastest route to the top of the 800 was with a law degree; only 3 of the 100 admit to being lawyers. The average member of the 800 sits on three corporate boards; the average member of the 100 hardly has time for his own.

Most of the 800 had been with their current company more than 22 years, putting in 15.9 years before they became CEO. Most of the INC. 100 have been with their company 12 years; since most were founders, they were CEO from Day 1.