Year	Number of
1980	4758
1981	5033
1982	4411
1983	4707
1984	4404
1985	5335
1986	6260
1987	7581
1988	8359
1989	9431
1990	12400
1991	14740
1992	14240
1993	17100
1994	19500
1995	19160
1996	20630
1997	20680
1998	22670
1999	24400
2000	23600
2001	26090
2002	24600
2003	25840
2004	27030
2005	25490
2006	25050
2007	24460