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 total U.S. population age 16 and over is at least 243 million. Subtracting the nearly 156 million Americans in the labor force in June 2013 -- that is, those who were either working or looking for work -- leaves 87 million Americans, which is close to 90 million.