They run regressions on
their entire set of countries, and on four different subgroups of countries, OECD countries, European
countries, and two alternative sets of Islamic countries. In general, they find support for the opportunity
cost theory of terrorism. In their full sample regression using real GDP per capita as one of the
independent variables, they find that lagged terrorism, real GDP per capita, openness, and population,
have positive and significant effects on terror, that the ratio investment to GDP, human capital, and
economic freedom have a negative and significant effects on terrorism, and, lastly, that the ratio of
government consumption to GDP does not appear to be relevant for terrorism.