At the undergraduate level, US-born engineering students constitute upwards of 90-95% of the student population (most foreign born candidates for engineering graduate schools are trained in their home countries). However, the pool of BS engineering graduates with US citizenship is much larger than the number who apply to engineering graduate schools. The proportion of foreign-born engineers among assistant professors younger than 35 years has increased from 10% in 1972 to 50%-55% in 1983–1985, illustrating a dramatic increase on US dependence on foreign-born students in the US college system. The increase in non-citizen assistant professors of engineering is the result of the fact that, in recent years, foreign-born engineers received close to 50 percent of newly awarded engineering doctorates (naturalized citizens accounted for about 4 percent) and, furthermore, they entered academe in disproportionately large numbers. 33% of all U.S. Ph.D.s in science and engineering are now awarded to foreign born graduate students as of 2004.