Year	Number
1970	4555419
1971	4688345
1972	5332608
1973	5742694
1974	6151773
1975	6832997
1976	7514696
1977	8171128
1978	9138296
1979	9697152
1980	10200000
1981	10700000
1982	11400000
1983	11900000
1984	12600000
1985	13300000
1986	14200000
1987	15000000
1988	15700000
1989	16400000
1990	18200000
1991	18700000
1992	19300000
1993	20300000
1994	21800000
1995	22900000
1996	23900000
1997	25200000
1998	26500000
1999	27800000
2000	28700000
2001	29400000
2002	30100000
2003	31300000
2004	31700000
2005	31800000
2006	31900000
2007	32100000
2008	32300000
2009	32800000
2010	32800000
2011	33700000
2012	33800000
2013	31700000
2014	31400000
2015	31600000
2016	31900000
2017	32200000
2018	32800000