Year	Number
1970	4388472
1971	4483918
1972	4746154
1973	5049850
1974	5317851
1975	5832204
1976	6346965
1977	6862970
1978	7457357
1979	7967015
1980	8463704
1981	8967598
1982	9520236
1983	10000000
1984	10600000
1985	11200000
1986	11900000
1987	12500000
1988	12900000
1989	13200000
1990	14500000
1991	14600000
1992	14700000
1993	15000000
1994	15900000
1995	16300000
1996	16800000
1997	17600000
1998	18500000
1999	19300000
2000	20100000
2001	20900000
2002	21600000
2003	23200000
2004	24100000
2005	24500000
2006	24900000
2007	25600000
2008	26100000
2009	27000000
2010	27600000
2011	28500000
2012	28900000
2013	28300000
2014	28100000
2015	28400000
2016	28700000
2017	29200000
2018	29800000