Year	Number
1970	3403624
1971	3535122
1972	3762259
1973	3928713
1974	3956003
1975	4198342
1976	4571183
1977	4982302
1978	5244498
1979	5277967
1980	5425422
1981	5453304
1982	5792307
1983	6083122
1984	6402580
1985	6884127
1986	7248069
1987	7806986
1988	8112095
1989	8172962
1990	8246567
1991	8282016
1992	8389395
1993	8838628
1994	9091994
1995	9353217
1996	9505960
1997	9944429
1998	10400000
1999	10100000
2000	11000000
2001	11300000
2002	11900000
2003	12600000
2004	13200000
2005	12900000
2006	13300000
2007	13600000
2008	14400000
2009	15000000
2010	15900000
2011	17100000
2012	18100000
2013	20400000
2014	20800000
2015	21500000
2016	21700000
2017	23200000
2018	23700000