This paper develops and estimates an economic model of physical activity that distinguishes between the participation and duration decisions (extensive and intensive margins). Results from IV estimators indicate that economic factors like income and opportunity cost of time are important determinants of physical activity and affect the participation and time spent decisions differently. Individuals with higher income are more likely to participate but, conditional on participation, spend less time engaged in physical activity. Individual characteristics like gender, race, marital status and having children also play an important role in the participation and duration decisions.
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