Year	Number of
1964	26450
1965	26970
1966	27210
1967	27540
1968	27980
1969	28550
1970	29290
1971	29790
1972	30270
1973	30670
1974	30940
1975	31310
1976	31360
1977	31360
1978	31100
1979	30780
1980	30180
1981	29410
1982	28760
1983	28230
1984	28050
1985	28170
1986	28520
1987	28700
1988	28640
1989	28480
1990	28480
1991	28360
1992	28480
1993	29020
1994	29490
1995	29820
1996	29750
1997	29590
1998	29370
1999	29140
2000	28800
2001	28300
2002	27990
2003	27930
2004	28050
2005	28110
2006	28200
2007	28310
2008	28420
2009	28610
2010	28640
2011	28420
2012	28140
2013	27870
2014	27620
2015	27440