Wonkblog cited a 2006 article from the Journal of Economic Perspectives about how life expectancies have risen across countries and over time. In The Determinants of Mortality, the authors note that poor countries with lower life expectancies have made major strides in closing the life expectancy gap with richer countries since World War II. They also note that higher incomes per se are not a cure-all; life expectancy gains mostly come from better nutrition, improved health infrastructure, and wider application of established medical technologies, which do not necessarily follow rising income levels.