When should a necessary inconvenience be introduced gradually, and when should it be imposed all at once? The question is crucial to web content providers, who in order to generate revenue must sooner or later introduce advertisements, subscription fees, or other inconveniences. Assuming that...

Data on 2,355 married women from the 2006 China Health and Nutrition Survey are used to study how female employment affects fertility in China. China has deep concerns with both population size and female employment, so the relationship between the two should be better understood. Causality...

Recent medical literature suggests that vitamin D supplementation protects against acute respiratory tract infection. Humans exposed to sunlight produce vitamin D directly. This paper investigates how differences in sunlight, as measured over several years across states and during the same...