...President Donald Trump has recommended a cut of some 30% to the State Department’s budget, which includes the funding for the U.S. Agency for International Development and most of America’s investments in global health. Congress is unlikely to go along with such large cuts, but our best guess is that, by the time the dust settles, key foreign-aid programs will be scaled back. Even modest cuts would represent the reversal of a long-term trend of increasing U.S. support for foreign aid, and a similar mood of retrenchment has taken hold elsewhere. In the U.K., the world’s second-largest aid donor, there...