NATIONAL BESTSELLERWhat if the challenge for humanity’s future is not too many people on a crowded planet, but too few people to sustain the progress that the world needs?Most people on Earth today live in a country where birth rates already are too low to stabilize the population: fewer than two children for every two adults. In After the Spike, economists Dean Spears and Michael Geruso sound a wakeup call, explai...