Year	Number of
1960	8955
1961	8906
1962	8794
1963	8686
1964	8669
1965	8777
1966	8926
1967	9231
1968	9600
1969	10020
1970	10480
1971	10930
1972	11440
1973	12000
1974	12660
1975	13420
1976	14130
1977	14810
1978	15300
1979	15550
1980	15570
1981	15330
1982	14950
1983	14600
1984	14440
1985	14400
1986	14550
1987	14880
1988	15070
1989	14720
1990	13710
1991	12220
1992	10000
1993	7726
1994	6376
1995	5881
1996	6518
1997	8805
1998	11770
1999	13960
2000	14940
2001	14900
2002	13850
2003	12370
2004	11000
2005	10040
2006	9613
2007	9456
2008	9433
2009	9346
2010	9065
2011	8473
2012	7808
2013	7149
2014	6653
2015	6299