High and/or swiftly rising public-debt-to-GDP ratios (debt) became significant issues in many developed democracies in recent years. Figure 1 plots gross, consolidated, central-government debt for 21 OECD countries, 1948–97.39 Fairly commonly, debt declined dramatically from 1948–72± and equally dramatically reversed thereafter. In many countries, debt doubled or more from 1972–90; in some, it now exceeds 100%. Wide and rising public concern over these developments, and the number of theories emerging to explain them, are thus hardly surprising. Beyond the common trend, however, lie large differences in postwar debt experiences of OECD nations. Shared cross-time variation comprises only 16.6% of the total, with increasing divergence apparent since 1980 while persistent cross-national differences represent 56.4% of the total variation. Even removing shared temporal fluctuations and country averages, considerable country-time-unique variation, 27% of the total, remains.