Military coups have gone out of fashion across most of the globe. In the 1970s, colonels in Greece could take over the government, but today, a military coup anywhere in Europe would be unthinkable. Even in Latin America—once the world's coup epicenter—such an act would likely be greeted with mockery. Only in Africa does the coup remain a recurring aspect of public life.

Patrick McGowan, a political scientist at Arizona State University, tracks African military coups—successful, unsuccessful, and aborted—in a study published recently in the quarterly Journal of Modern African Studies. The results are not pretty. From 1956 to 2001, only three nations (Botswana, Cape Verde, and Mauritius) did not experience any coups or coup attempts. Overall, 30 African nations experienced 80 successful coups in that period; all of these states, except for the Seychelles, also faced failed coups and plots. Yet coups usually settled nothing; rather, they encouraged other military factions to try their luck. Indeed, 89 percent of African coup attempts during this period targeted military regimes that had themselves staged successful coups earlier.

McGowan pinpoints West Africa as the region most prone to such military adventurism, but any new African regime, whether elected or put in place by force, faces significant risk. Worse yet, McGowan finds no indication of improvement: Coups in Africa occurred as frequently in the 1990s—purportedly the decade of democratization—as in supposedly bloodier decades. The only encouraging sign is their declining success rate, which fell from a peak of 74 percent between 1966 and 1970 to 38 percent in 1996-2001.

McGowan aims mainly to document this epidemic rather than explain it, and he certainly does a thorough job. But his article bypasses the key question: Why have coups...