Year	Number
1970	22000000
1971	22800000
1972	23600000
1973	24400000
1974	25300000
1975	25900000
1976	27400000
1977	28500000
1978	29200000
1979	31700000
1980	32700000
1981	33600000
1982	34600000
1983	35400000
1984	37100000
1985	36500000
1986	40600000
1987	41700000
1988	42300000
1989	42400000
1990	42300000
1991	42300000
1992	42500000
1993	43700000
1994	45400000
1995	46600000
1996	47700000
1997	47500000
1998	47000000
1999	46800000
2000	45800000
2001	46300000
2002	45700000
2003	45700000
2004	49300000
2005	50400000
2006	51700000
2007	53900000
2008	56200000
2009	57600000
2010	59500000
2011	60300000
2012	60600000
2013	65200000
2014	63500000
2015	61800000
2016	61100000
2017	62200000
2018	62500000