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This article employs the Cox proportional hazards model to discover the factors of survival of 162 party systems from 1792 to 2009. In order to avoid the endogeneity problem, the analysis employs the level of democracy as a control variable. The impact of the overall level of party system fragmentation is found negligible, even though excessive fragmentation is conducive to a higher hazard of party system termination. More importantly, systems with close competition among leading parties – including two-party systems and systems with close competition among up to four parties – are more likely to survive across time. The article introduces a methodological innovation by disaggregating the effective number of parties into two components, the leading parties’ balance and the residual fragmentation.