Year	Number
1975	31549984
1976	31794384
1977	31289058
1978	30814984
1979	29903984
1980	29320884
1981	28797476
1982	28720400
1983	29299344
1984	30599838
1985	32337516
1986	34461816
1987	36511540
1988	38255288
1989	38920828
1990	40581072
1991	40836012
1992	42183940
1993	42935548
1994	43743588
1995	44023388
1996	46121732
1997	44442664
1998	44671864
1999	44763648
2000	43134664
2001	41683976
2002	40597556
2003	38573904
2004	37383752
2005	35569032
2006	34104836
2007	31784678
2008	31253746
2009	31393340
2010	33300000
2011	32000000
2012	31900000
2013	31900000
2014	32100000
2015	33000000
2016	33600000
2017	34200000
2018	34700000