| Year | Total | vs prev |
|---|---|---|
| 2011 | 320 | −25.2% |
| 2010 | 428 | +0.5% |
| 2009 | 426 | −6.2% |
| 2008 | 454 | −16.4% |
| 2007 | 543 | +35.8% |
| 2006 | 400 | −21.4% |
| 2005 | 509 | −0.8% |
| 2004 | 513 | +0.6% |
| 2003 | 510 | +17.2% |
| 2002 | 435 | +11.3% |
| 2001 | 391 | +149.0% |
| 2000 | 157 | −47.1% |
| 1999 | 297 | −29.5% |
| 1998 | 421 | −26.1% |
| 1997 | 570 | — |