Duke 2008 | ASHE | Equity and Efficiency in Health and Healthcare

Many plausible explanations for the rise in obesity have been advanced, including declining rates of participation in physical activity, and a variety of policy interventions have been proposed to reduce obesity. There is a growing perception that an individual's decision about participating in physical activity has an important economic component because economics provides a framework for studying how people allocate their time to competing activities and what economic, environmental and demographic characteristics affect their decision to be physically active. This paper examines the economic determinants of participation in physical activity by developing and analyzing a two-stage consumer choice model of participation and by testing the predictions of the model using data drawn from the 2000 Behavioral Risk Factor Surveillance Survey (BRFSS).

Both the theoretical and empirical work emphasize that individuals make two distinct decisions: (1) the decision of whether or not to participate and (2) the decision of how long to participate (duration). We test the theoretical predictions about the effects of changes in income, opportunity cost of time and other exogenous factors on participation and time spent in physical activity by simultaneously estimating the participation and duration equations using maximum likelihood and correcting for selectivity. Not all individuals choose to participate in physical activity and this selectivity correction accounts for the statistical effects of this choice.

Higher income is associated with both a higher probability of participating and more time spent, but the size of the income effect is relatively small. The education and employment variables are proxies for the opportunity cost of time. The effect of changes in the opportunity cost of time on time spent in physical activity has a substitution and income effect that work in opposite directions. Employed persons are not more or less likely to participate but spend less time per week than unemployed persons indicating a dominating substitution effect. The probability of participation increases with level of education but duration is unaffected. This result is consistent with a human capital approach to health production in which more highly educated persons are more efficient at producing health.

The parameters on the race, gender and ethnicity show interesting patterns. Although blacks and Hispanics are less likely to participate in physical activity, those who do choose to participate do not spend more or less time in physical activity than whites. This suggests that interventions that increase the opportunity for participation, such as improved access to public parks or community programs, in diverse and disadvantaged communities may have a greater impact on physical activity than interventions aimed at increasing the amount of time spent per episode of physical activity. Females are less likely to participate in physical activity and those that do spend considerably less time participating than males.