The share of market output of the largest firms in the United Kingdom is in stark contrast to the United States. The top 10 firms in the United Kingdom, in 2000, pro duced 44% of all new housing, while in the United States, the market share for the top 10 producers was only 15%. Indeed, the top 100 producers in the United Kingdom accounted for 70% of new housing, while the corresponding figure for the United States was 29%.