This information probably exists in the academic literature, but I don't know the answers, even though I've read a lot of the "power elite" literature in sociology and economics and political science
* How long does a typical CEO serve in that position?
* How often are CEOs previously CEOs elsewhere, and how often do CEOs leave a position for another CEO position?
* Does the tenure of a typical CEO vary between publicly held companies and large privately held companies?
* How does CEO tenure differ between company founders and successor CEOs?
* How often are CEOs removed by a board of directors, both eventually and at some point? This may be complicated to discern as many CEOs who are forced out try to frame the event as a voluntary retirement. Does this differ for company founders and successor CEOs?
* What are the circumstances that most frequently cause a board of directors to fire a CEO?
* What are the circumstances that most frequently cause a CEO to leave a position as CEO unilaterally?
* How do CEO and top level politician career patterns differ between the for profit sector and the non-profit and government sector? Term limits and lots of study make this clear for U.S. Presidents and U.S. Governors. But what about members of Congress, Mayors, City Managers, County Managers, County elected officials, college presidents and chancellors, school superintendents and principals, football coaches, and other state and local elected officials and senior executives? What about non-profits and cooperatives?
* What are the statistics on the ages at which people become and cease to serve as CEOs and how does that differ by subtypes of CEOs?
* What characteristics of CEOs (age, education, experience, gender, etc.) differ between founders and successor CEOs, between publicly held and privately held company and non-profit CEOs, between elected officials and top appointed officials in government service, between private sector and elected top officials?