My basic research motivation has been to understand various real world conditions. Some of the things I've studied are:

• the reasons for the limited spread of modern economic growth;
• the relation of economic growth to happiness;
• happiness in the transition from socialism to capitalism;
• life cycle happiness;
• the transition from high to low mortality and fertility that has invariably accompanied modernization;
• "long swings" of 15 to 25 years in population and economic growth in the US and other developed countries;
• the post-World War II American baby boom and bust.

Progress on these problems has often involved empirical work to establish more clearly the facts to be explained - such as happiness trends, regional incomes in 19th century U.S., reconstructing the history of America's childbearing behavior, and establishing the rise of school enrollments in countries throughout the world. It has required the use of economic theory to organize data and formulate hypotheses, and led to new theorizing on topics such as childbearing behavior and subjective well-being. It has also called for work in other social sciences and for learning new techniques and concepts that fall outside the purview of economics, such as demographic methodology and theories of "relative deprivation", "natural" (i.e. unregulated) fertility, and hedonic adaptation.

Currently I am studying rural-urban differences in subjective well-being.  A new book, Happiness, Growth and the Life Cycle (Oxford University Pres, 2010) brings together some of my recent work.