Year	Number
1970	4069987
1971	4180496
1972	4808296
1973	5201464
1974	5586219
1975	6237722
1976	6885291
1977	7498076
1978	8426304
1979	8946012
1980	9424481
1981	9830125
1982	10400000
1983	10800000
1984	11400000
1985	12000000
1986	12900000
1987	13500000
1988	14100000
1989	14700000
1990	16400000
1991	16800000
1992	17300000
1993	18100000
1994	19500000
1995	20400000
1996	21200000
1997	22300000
1998	23500000
1999	24600000
2000	25500000
2001	26000000
2002	26600000
2003	27500000
2004	27800000
2005	27700000
2006	27700000
2007	27700000
2008	27900000
2009	28200000
2010	28100000
2011	28900000
2012	28800000
2013	26700000
2014	26300000
2015	26500000
2016	26800000
2017	27100000
2018	27400000