Year	Number
1961	550
1962	600
1963	700
1964	900
1965	1200
1966	1350
1967	1450
1968	1500
1969	1544
1970	1600
1971	1650
1972	1700
1973	1750
1974	1800
1975	1850
1976	1900
1977	1950
1978	2000
1979	2050
1980	2150
1981	2290
1982	2460
1983	2570
1984	2710
1985	2870
1986	3010
1987	3150
1988	4650
1989	5000
1990	5900
1991	4010
1992	3867
1993	3850
1994	3800
1995	3750
1996	3700
1997	3669
1998	3357
1999	3648
2000	2688
2001	3165
2002	3133
2003	2957
2004	3068
2005	2913
2006	2816
2007	2835
2008	3371