In New York City, the population has increased drastly over the last two centuries, although Manhattans population is slowly starting to decline since the twentieth century. Other districts have not had this problem, with their population increasing six times in the last century. Overall, the districts in New York City have been increasing rapidly, except for the Manhattan district.
Manhattans started off with being the most populated district in New York City, making up more than half the population. As time passed, more people began migrating to New York, and living in other districts rather than living in Manhattan. This led to Manhattan eventually becoming one of the less populated districts.
The decline in the population of Manhattan over the years could be due to many reasons. It could be that it had become so crowded that people began moving to other districts, and it could also be that Manhattan had just lost popularity, with other districts becoming more civilized.