A comparison of pension fund asset allocations around the globe shows surprisingly wide variations. Closer study reveals some interesting relationships that help explain the variations. Outright allocation restrictions are numerous, but they appear to be constraining in only a few situations. Pension funds diversify internationally to a much greater degree in equities than in bonds. A positive relationship exists between a country's relative level of international trade and its average level of international diversification within equities. The most dramatic finding is that subtle accounting and regulatory differences between countries have a strong impact on the allocation between equities and bonds.