My dissertation proposes a theory that explains the circumstances under which leaders can come to power who have a very large impact on the organizations they lead. The first stage focuses on how leaders are chosen. Every organization has a process by which leaders come to power. This process judges candidates for leadership on a combination of their intrinsic characteristics and random factors that affect their ability to gain power.
If random factors play only a small role in this process, then any individual leader is likely to be fungible, because if he had not gained power the person who would have is likely to have had very similar characteristics. If, however, random factors play a large part in this process, then the possibility exists that the leader who gains power will have decision-making characteristics very different from those of other potential leaders, and thus may make decisions very different from those other leaders might have made. Such very different leaders are "Outlier" leaders. The theory suggests how to determine if a leader came to power through a process likely to produce an Outlier leader. If an Outlier leader comes to power, his influence on events will be constrained by both his power within the state and his state's position within the international system. The second stage of the theory assesses these constraints on leader discretion. If constraints are low, an Outlier leader is particularly likely to have a large impact on his state, and perhaps even the entire international system. Unconstrained Outlier leaders are likely to be very distinct from normal ones. Most importantly, they are likely to display very high variance in performance, performing either very well or very poorly when they are in power. The theory is tested quantitatively using historians' rankings of the performance of Presidents of the United States, and qualitatively using case studies of three U.S. Presidents: Jefferson, Lincoln, and Wilson, and two British Prime Ministers: Chamberlain and Churchill. The theory's relevance beyond democratic political leaders is also examined using eight shadow cases including four dictators, two businessmen, a military leader, and a scientist.