Year	Number
1970	7567533
1971	8789128
1972	10200000
1973	11400000
1974	13900000
1975	15000000
1976	16200000
1977	17300000
1978	18200000
1979	28000000
1980	28800000
1981	29400000
1982	30200000
1983	31000000
1984	31700000
1985	22500000
1986	33300000
1987	34100000
1988	35000000
1989	35900000
1990	36800000
1991	38000000
1992	39200000
1993	40200000
1994	41600000
1995	43000000
1996	44600000
1997	45600000
1998	47400000
1999	49200000
2000	50900000
2001	51500000
2002	52800000
2003	51200000
2004	52400000
2005	52800000
2006	52900000
2007	52500000
2008	53000000
2009	53700000
2010	54100000
2011	54400000
2012	54200000
2013	56100000
2014	55800000
2015	55400000
2016	55500000
2017	55300000
2018	54800000