Here's NAHB's Eye on Housing on the Builder 100 share of total home building in the U.S.:
From 2009 to 2015, the market share of closings for the top 20 builders increased by 9.3%, and the market share among the top 50 builders increased by 10.7% over the same period.
The number of closings among the top 100 builders ranged from 36,736 for the top builder in 2015, D.R. Horton, to 365 total closings for the 100th largest builder. The number of closings for the top 20 builders ranged from 36,736 to 2,422 for the 20th largest builder. The number of closings for the top 50 builders ranged from 36,736 to 900 closings for the 50th largest builder.