A comprehensive study of civil war was carried out by a team from the World Bank in the early 21st century. The study framework, which came to be called the Collier–Hoeffler Model, examined 78 five-year increments when civil war occurred from 1960 to 1999, as well as 1,167 five-year increments of "no civil war" for comparison, and subjected the data set to regression analysis to see the effect of various factors. The factors that were shown to have a statistically significant effect on the chance that a civil war would occur in any given five-year period were: