Year	Number
1970	35900000
1971	46600000
1972	52500000
1973	57800000
1974	57200000
1975	60300000
1976	69900000
1977	84800000
1978	95500000
1979	95000000
1980	89800000
1981	87200000
1982	81800000
1983	80300000
1984	79900000
1985	83000000
1986	86000000
1987	89500000
1988	90500000
1989	88900000
1990	85700000
1991	86100000
1992	87400000
1993	88800000
1994	89800000
1995	93900000
1996	99700000
1997	102000000
1998	109000000
1999	113000000
2000	118000000
2001	123000000
2002	129000000
2003	136000000
2004	140000000
2005	140000000
2006	140000000
2007	140000000
2008	138000000
2009	137000000
2010	135000000
2011	134000000
2012	132000000
2013	131000000
2014	129000000
2015	130000000
2016	128000000
2017	129000000
2018	131000000