statistically significant for women in both the short and medium-term. De Mel et al. (2012) is the other study with high power. They find no impact of training alone on profits of existing firms over either the short or medium run, but do find significant impacts of the combination of training and a grant on shortrun profits, with these gains dissipating over time. In a separate sample of women who were out of the labor force at baseline, training is found to significantly increase profits and sales of start-up businesses by approximately 40 percent, although the confidence intervals are wide around this level.

Calderon et al. (2012) finds a 24 percent increase in weekly profits and 20 percent increase in weekly revenues, both significant at the 10 percent level. However, given that attrition is 26 percent by the second round survey, and that 50 percent of the non-attritors have closed down, there is reason to be cautious in interpreting this estimate of the impact on surviving non-attriting firms. Valdivia (2012), the only other study to find significant impacts on revenues, finds a 20 percent increase for the treatment group that got both training and intensive one-on-one technical assistance, but no significant increase from the training alone. Finally, Glaub et al. (2012) find a positive effect of their personal initiative training on sales one year later, although they do not survey the non-compliers (individuals selected for training who do not attend), which is problematic if there is selective participation. (The authors note illness and unforeseen business problems were reasons for non-attendance.) Several studies have emphasized the possibility that business training may have its strongest impact on sales during a bad month. The working paper version of Karlan and Valdivia (2011) stressed this avenue, noting that training might help clients identify strategies to reduce downward fluctuations in sales by thinking about diversifying the products they offer as well as being more proactive about alternative activities during slow months. Their difference-in-difference estimate finds a 30 percent increase in sales during a bad month. However, the published version of the paper de-emphasizes this impact, noting that when their preferred ANCOVA specification is used instead of difference-in-differences, the impact falls to an insignificant 5 to 7 percent increase. The possibility that training may be particularly valuable during bad times is also emphasized by Drexler et al. (2012), who find that their rule of thumb training leads to an increase in sales during bad weeks which is significant at the 10 percent level. However, Drexler et al. also ask firm owners to report sales in a bad month and find a very small and insignificant impact of training on this measure. Giné and Mansuri (2012), de Mel et al. (2012), and Valdivia (2012) also find no significant impacts of training alone on sales during bad months. Viewing these studies together therefore leads us to conclude that the evidence that training has particularly strong effects during bad periods is weak.

Since the costs of training often increase less than proportionally with the size of the firms taking training, subsistence microenterprises would likely need to see much higher percentage increases in profits from training to make training worthwhile than would larger firms. Nevertheless, a firm earning $1 per day would need to see only a 13.7 percent increase in profits for the cost of $100 of training to be recouped over two years. We see that the confidence intervals for the studies which do look at profits are almost all wide enough to include this level of return. For larger firms, the percentage increase in 16