Year	Number of
1970	13250
1971	13500
1972	13750
1973	14000
1974	14300
1975	14620
1976	14990
1977	15380
1978	15360
1979	14710
1980	13670
1981	12410
1982	11320
1983	10470
1984	10080
1985	9893
1986	10200
1987	10720
1988	11240
1989	11490
1990	11460
1991	11280
1992	11030
1993	10670
1994	10200
1995	9535
1996	8912
1997	8378
1998	7948
1999	7778
2000	7807
2001	7781
2002	7595
2003	7341
2004	7113
2005	6965
2006	6660
2007	6379
2008	6001
2009	5715
2010	5470
2011	5273
2012	5179
2013	5096
2014	4923
2015	4797