Complex sentence: These numbers increased dramatically during the 1980s, so that the census estimated that there were 147,375 people by 1990, and the group continued to grow, somewhat more slowly, to 167,792 by 2000.
Split into simpler sentences: These numbers increased dramatically during the 1980s, so that the census estimated that there were 147,375 people by 1990. The group continued to grow, somewhat more slowly, to 167,792 by 2000.