The Private Charitable Generosity Index, hereafter referred to simply as the Generosity Index, attempts to quantify a rather ambiguous concept - personal generosity. The Generosity Index is based on three measures: percentage of donors to tax filers, charitable donations as a percent of private income, and per capita volunteer hours. Each measures generosity in a different way. The index itself is a compilation of these three measures of generosity.

All of the data compiled for the Generosity Index refer to registered charities. That is, the compilation of information excludes non-profit organizations that are not registered charities, and informal activities.