Year	Number of
1965	22930
1966	23390
1967	23660
1968	23880
1969	24000
1970	24070
1971	24170
1972	24340
1973	24640
1974	25160
1975	25900
1976	26790
1977	27980
1978	29240
1979	30420
1980	31300
1981	31660
1982	31780
1983	31780
1984	31670
1985	31620
1986	31460
1987	31420
1988	31460
1989	31560
1990	31520
1991	31570
1992	31740
1993	32130
1994	32800
1995	33480
1996	34120
1997	34590
1998	35040
1999	35260
2000	35490
2001	35550
2002	35470
2003	35380
2004	35190
2005	34980
2006	34530
2007	33840
2008	33060
2009	32350
2010	31620
2011	30940
2012	30360
2013	29960
2014	29840
2015	29740