Levene enrolled at Columbia University and in his spare time conducted biochemical research, publishing papers on the chemical structure of sugars. In 1896 he was appointed as an Associate in the Pathological Institute of the New York State Hospitals, but he had to take time off to recuperate from tuberculosis.
This graph shows the median age of the resident population of the United States from 1960 to 2015. In 2015, the median age of the United States population was approximately 37.7 years.
The American population almost quadrupled during the 20th centuryâat a growth rate of about 1.3% a yearâfrom about 76 million in 1900 to 281 million in 2000. It reached the 200 million mark in 1968, and the 300 million mark on October 17, 2006.