Event History Analysis

Event history analysis allows researchers to investigate not only occurrences of certain political events but also the processes or histories of those events. In essence, event history analysis estimates how histories of events or durations leading up to the events (if events occur at all) change with different values of independent variables (or covariates). Such estimates allow researchers to discuss how included covariates increase or decrease the probability of the event occurrence at any given time. Since event history analyzes the duration between the start when the event is possible to the [Page 856]time when the event actually occurs (if it occurs), event history analysis is often called duration analysis. Alternatively, as event history analysis models the probability of an observation surviving (not experiencing the event), event history analysis is sometimes called survival analysis. Below, this entry discusses some major features and possible applications of event history analysis, taking into account both parametric and nonparametric models and some recent extensions.

Many political science studies ask questions regarding occurrences of significant political events. For instance, scholars in comparative politics are interested in why some countries democratize while others fail to do so (democratization), or why some countries are able to economically develop while others stay in poverty (economic development). Likewise, scholars in international relations study why some countries join many international organizations, while others join only a few (international organization [IO] membership) and why some pairs of states are more likely to engage in militarized interstate disputes than others (militarized disputes). Scholars in American politics ask why some court nominees are approved, while others are not (legislative and judicial branch relations), and what makes an incumbent more likely to face a challenger (reelection). By answering these questions, political scientists are able to identify systematic dynamics influencing occurrences of these political events.

While these inquiries certainly enhance our understanding of interesting political phenomena, the timing of occurrences of such events can provide even richer information and thus help further enhance our understanding of the underlying dynamics. For instance, not only identifying under what conditions a country is able to democratize but also finding out under what conditions a country is able to do so faster than other countries would help promote our understanding of democratization. Event history analysis provides researchers with a unique opportunity to exploit richer information of the histories of events.

Since event history analysis has been introduced to political science, there have been a growing number of studies that use it in empirical investigations. With this powerful new tool, many old research questions have been revisited, and many new research questions have been developed and empirically tested. These questions cut across sub-disciplines of political science, and examples of them are numerous. Why do some coalition governments last longer than others? Why do some militarized disputes last longer than others? Why do some periods of peace last longer than others? Why do some economic sanctions last longer than others? Why do some drugs take a longer time to get approved by the Food and Drug Administration than other drugs? And why can some representatives maintain their seats longer than others? The popularity of the event history analysis is due to its usefulness in understanding the underlying political dynamics of events and their histories. Specifically, event history analysis has a few advantages over traditional binary logit or probit analysis, on the one hand, and over ordinary least squares regression (OLS), on the other.

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