Year	Number
1975	17068056
1976	17184520
1977	16866152
1978	16554747
1979	16044546
1980	15745183
1981	15455301
1982	15366329
1983	15685299
1984	16353153
1985	17296064
1986	18407068
1987	19514266
1988	20379836
1989	20866758
1990	21715482
1991	21798202
1992	22516860
1993	22903456
1994	23370376
1995	23884920
1996	25113316
1997	24228904
1998	24256530
1999	24096024
2000	23389052
2001	22663120
2002	22254656
2003	21163088
2004	20464990
2005	19561608
2006	18708284
2007	18026930
2008	17561504
2009	17552676
2010	18500000
2011	17800000
2012	17600000
2013	17600000
2014	17600000
2015	18200000
2016	18500000
2017	19000000
2018	19300000