The hypothesis gave birth to what would become the first formal consumption function. However, Kuznets shook the economic world by finding that Keynes' predictions, while seemingly accurate in short-run cross-sections, broke down under more rigorous examination. In his 1942 tome "Uses of National Income in Peace and War", published by the National Bureau of Economic Research, Kuznets became the first economist to show that the Absolute Income Hypothesis gives inaccurate predictions in the long run (by using time-series data). Keynes had predicted that as aggregate income increases, so will marginal savings. Kuznets used new data to show that, over a longer span of time (1870s – 1940s) the savings ratio remained constant, despite large changes in income. This paved the way for Milton Friedman's permanent income hypothesis, and several more modern alternatives such as the life-cycle hypothesis and the relative income hypothesis.