Year	Number
1970	8144621
1971	9309038
1972	10800000
1973	11900000
1974	14500000
1975	15700000
1976	17000000
1977	18200000
1978	19300000
1979	29100000
1980	30000000
1981	30600000
1982	31300000
1983	32200000
1984	32800000
1985	23700000
1986	34500000
1987	35300000
1988	36200000
1989	37100000
1990	37900000
1991	39100000
1992	40200000
1993	41100000
1994	42400000
1995	43900000
1996	45400000
1997	46500000
1998	48300000
1999	50100000
2000	51800000
2001	52500000
2002	53800000
2003	52200000
2004	53400000
2005	53900000
2006	53900000
2007	53500000
2008	54100000
2009	54700000
2010	55100000
2011	55400000
2012	55100000
2013	57000000
2014	56800000
2015	56300000
2016	56400000
2017	56200000
2018	55700000