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.
At age 30, 75% of people will have at least one surviving grandparent. Since 1900, the percentage of Americans 65 years and older has more than tripled (4.1% in 1900 to 12.7% in 1999). In 1900 there were 3.1 million people 65 years and older; in 1999 that number had risen to 34.5 million.