John Maynard Keynes was an English economist born in 1883 who attended Cambridge University. During the Great Depression in the 1930s, all classical economic theories were proved wrong as unemployment rose to 25% and output declined by 50%. Keynes proposed new economic philosophies that the economy should be viewed in the short-run, government intervention is necessary to increase consumption and public debt should not exceed 50% of GDP. By applying these theories, industrialized economies were able to recover from the worst economic downturn in history.