Year	Number
1961	750
1962	800
1963	850
1964	900
1965	950
1966	1000
1967	1100
1968	1300
1969	1500
1970	2072
1971	2270
1972	2470
1973	2660
1974	2860
1975	3050
1976	3250
1977	3454
1978	3500
1979	3500
1980	3500
1981	3350
1982	3200
1983	3075
1984	2950
1985	2800
1986	2700
1987	2580
1988	2450
1989	2300
1990	2180
1991	2050
1992	1925
1993	1800
1994	1675
1995	1550
1996	1400
1997	1300
1998	1200
1999	1080
2000	1000
2001	900
2002	800
2003	700
2004	450
2005	1555
2006	3000