Why do so few young scientists get NIH funding?

WSJ.com : Scientific revolutions are often led by the youngest scientists, and yet such innovation in the US could be at risk, says Jonah Lehrer in the Wall Street Journal, as the number of successful young scientists is dramatically shrinking.In 1980, the largest share of grants from the National Institutes of Health went to scientists in their late 30s. By 2006 the curve had been shifted sharply to the right, with the highest proportion of grants going to scientists in their late 40s. This shift came largely at the expense of young scientists.In 1980, researchers between the ages of 31 and 33 received nearly 10% of all grants; by 2006 they accounted for approximately 1%. And the trend shows no signs of abating: In 2007, the most recent year available, there were more grants to 70-year-old researchers than there were to researchers under the age of 30.