Challenge.gov, which celebrated its fifth anniversary this fall, is a federal website that showcases requests by government agencies for the public to tackle hard problems in exchange for cash prizes and other incentives. Since its inception in 2010, agencies have run more than 450 challenges to help ameliorate problems such as decreasing the "word gap" between children from high- and low-income families or increasing the speed at which salt water can be turned into fresh water for farming in developing economies.
