| Residency | Year | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | |
| Total | 30 | 31 | 32 | 40 | 40 | 52 | 52 | 50 | 52 | 66 |
| U.S. Resident | 29 | 30 | 31 | 40 | 39 | 50 | 51 | 49 | 51 | 63 |
| Nonresident Alien | - | - | - | - | 1 | 2 | 1 | 1 | 1 | 3 |
| Unknown | 1 | 1 | 1 | - | - | - | - | - | - | - |
| Total (%) | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% |
| U.S. Resident | 96.7% | 96.8% | 96.9% | 100.0% | 97.5% | 96.2% | 98.1% | 98.0% | 98.1% | 95.5% |
| Nonresident Alien | - | - | - | - | 2.5% | 3.8% | 1.9% | 2.0% | 1.9% | 4.5% |
| Unknown | 3.3% | 3.2% | 3.1% | - | - | - | - | - | - | - |