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.
Since the 1960's the growth of the U.S. population aged over 65 has been twice that of the general population. By the year 2000, the number of men and women over age 65 in the U.S. is projected to increase to 32 million people, which will be approximately 20% of the population.