By 2025, the world's population will have grown by another 1.8 billion or so, bringing it to roughly 8 billion. Ninety-five percent of the increment will be in what today are called developing countries; only 5 percent will be in the rich industrialized countries. Indeed, birth rates have fallen...

Two contemporary issues provide reason to focus on national saving and investment: the debate over public pensions, and pensions more generally, in all rich countries; and the large global current account imbalances, conceptually the difference between national savings and domestic investment....