Year	Number
1970	3054945
1971	3158932
1972	3333802
1973	3504027
1974	3639757
1975	3895377
1976	4164829
1977	4469961
1978	4787301
1979	5144067
1980	5555327
1981	5982610
1982	6160968
1983	6467020
1984	6781752
1985	6887905
1986	7032449
1987	7205496
1988	7553074
1989	7682072
1990	7880673
1991	8238377
1992	8386435
1993	8605506
1994	9080904
1995	9637351
1996	10000000
1997	10300000
1998	11200000
1999	12000000
2000	12300000
2001	13400000
2002	14400000
2003	15500000
2004	17100000
2005	18600000
2006	20500000
2007	22200000
2008	24400000
2009	26300000
2010	28500000
2011	30500000
2012	32400000
2013	34200000
2014	35600000
2015	36800000
2016	38000000
2017	39400000
2018	40900000