Year	Number of
1956	44210
1957	42670
1958	41030
1959	39650
1960	38850
1961	38760
1962	39500
1963	40650
1964	41800
1965	42680
1966	42920
1967	43080
1968	43160
1969	43210
1970	43400
1971	43530
1972	43750
1973	44000
1974	44340
1975	44750
1976	45140
1977	45490
1978	45870
1979	46090
1980	46160
1981	45950
1982	45680
1983	45430
1984	45140
1985	44760
1986	44360
1987	43800
1988	43020
1989	42180
1990	41340
1991	40220
1992	39180
1993	38170
1994	37090
1995	35900
1996	34890
1997	33860
1998	32830
1999	31590
2000	30190
2001	28630
2002	27050
2003	25330
2004	23730
2005	22250
2006	21030
2007	19930
2008	18950
2009	17900
2010	16870
2011	15680
2012	14600
2013	13580
2014	12800
2015	12250