Year	Number of
1959	13870
1960	13820
1961	14030
1962	14430
1963	14800
1964	15120
1965	15260
1966	15250
1967	15080
1968	14900
1969	14620
1970	14360
1971	14100
1972	13800
1973	13510
1974	13330
1975	13250
1976	13240
1977	13320
1978	13360
1979	13470
1980	13520
1981	13520
1982	13590
1983	13590
1984	13490
1985	13220
1986	12650
1987	11880
1988	11030
1989	10260
1990	9651
1991	9260
1992	9049
1993	8958
1994	8888
1995	8831
1996	8688
1997	8544
1998	8401
1999	8267
2000	8146
2001	8028
2002	7951
2003	7902
2004	7845
2005	7765
2006	7693
2007	7651
2008	7590
2009	7537
2010	8161
2011	7301
2012	7125
2013	6935
2014	6733
2015	6537