Two-thirds of American marriages are between an older man and a younger woman. Is that a bad thing? The conventional wisdom suggests so. But evidence shows that age-gap relationships are relatively happy; indeed, according to our estimates, an age gap of five years is associated with the relationship lasting longer.

China has launched the biggest purge of its armed forces since 1971, alongside a huge increase in actions against party members and officials. The question left for international observers is what this means for China’s readiness to launch an invasion of Taiwan. We report on why Xi Jinping’s purge should worry the world.