Year	Number of
1954	19570
1955	19460
1956	19220
1957	18950
1958	18770
1959	18600
1960	18410
1961	18320
1962	18310
1963	18410
1964	18580
1965	18750
1966	19040
1967	19410
1968	19860
1969	20320
1970	20800
1971	21210
1972	21620
1973	22110
1974	22510
1975	22910
1976	23310
1977	23670
1978	24020
1979	24470
1980	25050
1981	25570
1982	26130
1983	26690
1984	27190
1985	27500
1986	27600
1987	27520
1988	27330
1989	27190
1990	26880
1991	26620
1992	26430
1993	26140
1994	26100
1995	26540
1996	27570
1997	28990
1998	30630
1999	32360
2000	33960
2001	35330
2002	36400
2003	37410
2004	38220
2005	38790
2006	38810
2007	38750
2008	38300
2009	37830
2010	37310
2011	36540
2012	35760
2013	35100
2014	34430
2015	33740