Year	Number
1970	7023154
1971	8157426
1972	9528090
1973	10600000
1974	13200000
1975	14400000
1976	15600000
1977	16800000
1978	17800000
1979	27600000
1980	28400000
1981	29000000
1982	29800000
1983	30500000
1984	31000000
1985	21900000
1986	32600000
1987	33400000
1988	34300000
1989	35200000
1990	36100000
1991	37100000
1992	38200000
1993	39400000
1994	40700000
1995	42100000
1996	43700000
1997	45000000
1998	46600000
1999	48300000
2000	49900000
2001	50500000
2002	51800000
2003	50100000
2004	51300000
2005	51700000
2006	51700000
2007	51300000
2008	51900000
2009	52600000
2010	52900000
2011	53300000
2012	53100000
2013	54800000
2014	54600000
2015	54200000
2016	54300000
2017	54100000
2018	53500000