Year	Number
1970	97778184
1971	100938448
1972	99392000
1973	92078360
1974	90901376
1975	88291896
1976	88004120
1977	90712528
1978	98536992
1979	98441128
1980	95957824
1981	92212512
1982	90196104
1983	88906664
1984	87054480
1985	83068088
1986	78827208
1987	77060952
1988	73784264
1989	70153824
1990	71874488
1991	71120568
1992	71937440
1993	71770184
1994	72869024
1995	77509312
1996	80223360
1997	82042008
1998	77804008
1999	70345112
2000	65450512
2001	62636936
2002	61276352
2003	53140780
2004	49330056
2005	45567688
2006	46238288
2007	39122044
2008	39300004
2009	40316048
2010	40600000
2011	40900000
2012	39500000
2013	38400000
2014	37900000
2015	38700000
2016	37900000
2017	37600000
2018	37000000