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.
In the United States, the declines have occurred among all age groups, but are most dramatic among young adults. Today, just 20% of adults ages 18 to 29 are married, compared with 59% in 1960. Over the course of the past 50 years, the median age at first marriage has risen by about six years for both men and women.