The modern study of religion and economics begins with Adam Smith's An Inquiry into the Nature and Causes of the Wealth of Nations (1776). Smith applied his economic analysis to several aspects of religion that researchers have since developed with quantitative research. Smith's fundamental contribution to the study of religion was that religious beliefs and activities are rational choices. As in commercial activity, people respond to religious costs and benefits in a predictable, observable manner. People choose a religion and the degree to which they participate and believe (if at all).