Year	Number
1961	1700
1962	1900
1963	2100
1964	2200
1965	2300
1966	2400
1967	3000
1968	3500
1969	4462
1970	4848
1971	5820
1972	7980
1973	8100
1974	8200
1975	8900
1976	9800
1977	9800
1978	9900
1979	9400
1980	9600
1981	9700
1982	9900
1983	9900
1984	10000
1985	10100
1986	10300
1987	9800
1988	9700
1989	9500
1990	9182
1991	10451
1992	10520
1993	10600
1994	10680
1995	10760
1996	10840
1997	10920
1998	11000
1999	11039
2000	11856
2001	12500
2002	13100
2003	13680
2004	16639
2005	18127
2006	19615
2007	22590
2008	25564