The"distance effect"measuring the elasticity of trade flows to distance has been rising since the early 1970s in a host of studies based on the gravity model, leading observers to call it the"distance puzzle". This paper reviews the evidence and explanations. Using an extensive data set of 124...

Onchocerciasis is a devastating African parasitical disease that causes severe debilitation and intense itching. By the time its victims are in their late twenties, they experience impaired vision, often blindness. Millions continued to succumb to the disease until the onchocerciasis control...