| Year | East region | Middle region | West region | |||
| Amount | Proportion | Amount | Proportion | Amount | Proportion | |
| 2003 | 144.0 | 81.4 | 25.9 | 14.7 | 7.0 | 4.0 |
| 2004 | 156.5 | 82.4 | 27.4 | 14.4 | 6.0 | 3.2 |
| 2005 | 153.2 | 85.4 | 17.5 | 9.8 | 8.7 | 4.9 |
| 2006 | 191.3 | 89.8 | 13.9 | 6.5 | 7.9 | 3.7 |
| 2007 | 237.5 | 85.7 | 25.7 | 9.3 | 13.8 | 5.0 |
| 2008 | 338.9 | 82.6 | 33.9 | 8.3 | 37.6 | 9.2 |
| 2009 | 390.2 | 84.7 | 26.2 | 5.7 | 44.4 | 9.6 |
| 2010 | 501.1 | 82.7 | 41.3 | 6.8 | 63.3 | 10.5 |
| 2011 | 580.5 | 81.3 | 45.0 | 6.3 | 88.6 | 12.4 |
| 2012 | 536.5 | 81.8 | 60.2 | 9.2 | 59.0 | 9.0 |