Why did population growth in britain lead to colonization in america?

If there was one inarguable fact about the American colonies in the mid - to late 18th century, it was that they were growing like crazy. In 1730, the population of the 13 colonies was about 655,000. Boston was the biggest city, with a population of about 13,000, while New York and Philadelphia were home to about 8,500 people each.

By 1760, the population had reached 1.6 million, not including African slaves, and by 1775, the white population stood at 2.5 million. Philadelphia was the largest city in that year, with a population of about 34,000.