| Residency | Year | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | |
| Total | 38 | 111 | 203 | 284 | 382 | 548 | 640 | 700 | 686 | 630 |
| U.S. Resident | 38 | 111 | 203 | 284 | 380 | 546 | 637 | 696 | 683 | 627 |
| Nonresident Alien | - | - | - | - | 1 | 1 | 2 | 3 | 2 | 2 |
| Unknown | - | - | - | - | 1 | 1 | 1 | 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 | 100.0% | 100.0% | 100.0% | 100.0% | 99.5% | 99.6% | 99.5% | 99.4% | 99.6% | 99.5% |
| Nonresident Alien | - | - | - | - | 0.3% | 0.2% | 0.3% | 0.4% | 0.3% | 0.3% |
| Unknown | - | - | - | - | 0.3% | 0.2% | 0.2% | 0.1% | 0.1% | 0.2% |