Year	Number
1970	59900000
1971	60600000
1972	61600000
1973	62900000
1974	64000000
1975	64500000
1976	64600000
1977	64700000
1978	64300000
1979	63900000
1980	63500000
1981	63100000
1982	62400000
1983	62000000
1984	62000000
1985	62200000
1986	62600000
1987	62800000
1988	62700000
1989	62800000
1990	62700000
1991	62800000
1992	62800000
1993	63900000
1994	64300000
1995	64900000
1996	64600000
1997	65200000
1998	67400000
1999	68300000
2000	70000000
2001	70800000
2002	71100000
2003	70600000
2004	66400000
2005	64800000
2006	63900000
2007	62400000
2008	61000000
2009	60100000
2010	59300000
2011	58200000
2012	57300000
2013	59900000
2014	59900000
2015	59500000
2016	59600000
2017	60400000
2018	60900000