Year	Number of
1974	46910
1975	46570
1976	45800
1977	44960
1978	43900
1979	43200
1980	42860
1981	42880
1982	43370
1983	44200
1984	44970
1985	45920
1986	46360
1987	46760
1988	46990
1989	46750
1990	46470
1991	45900
1992	45340
1993	43900
1994	41810
1995	38560
1996	34410
1997	29620
1998	24740
1999	21050
2000	18600
2001	17610
2002	17440
2003	18030
2004	18780
2005	19280
2006	19580
2007	19720
2008	19950
2009	19970
2010	19920
2011	19790
2012	19400
2013	19030
2014	18440
2015	17930