Year	Number of
1990	0
1991	0
1992	2
1993	5
1994	13
1995	39
1996	109
1997	280
1998	689
1999	1610
2000	3444
2001	5960
2002	8376
2003	10140
2004	11320
2005	11980
2006	12500
2007	12860