Current methods of cost effectiveness analysis implicitly assume zero spillovers among social ties. This can underestimate the benefits of health interventions and misallocate resources toward interventions with lower comprehensive effects. We discuss the implications of social spillovers for program evaluation and document the first evidence of causal spillovers of health behaviors between spouses by leveraging experimental data from the Lung Health Study (smoking) and COMBINE Study (drinking). We find large decreases in spousal substance use from treatments with a therapy component, which reduces the incremental cost effectiveness ratios of some treatments by 12 to 18 percent.

Using a dataset of 274 male Thoroughbred racehorses in the United States, we study the effect of age on racing performance. Beyer speed figures, which are uniform measures of racing performance across distance and racing surface, are utilized in this study. A system of equations is estimated to determine quadratic improvement and decline in racing performance. We find that a typical horse’s peak racing age is 4.45 years. The rate of improvement from age 2 to 4 1/2 is greater than the rate of decline after age 4 1/2. A typical horse will improve by 10 (horse) lengths in sprints (less than 1 mile) and 15 lengths in routes (one mile or greater) from age 2 to 4 1/2. Over the next five years the typical decline is 6 lengths for sprints and 9 1/2 lengths for routes.

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