Year	Number
1970	56500000
1971	64500000
1972	71100000
1973	76700000
1974	77200000
1975	79800000
1976	88700000
1977	103000000
1978	113000000
1979	120000000
1980	113000000
1981	110000000
1982	103000000
1983	100000000
1984	99600000
1985	92300000
1986	105000000
1987	108000000
1988	109000000
1989	108000000
1990	107000000
1991	108000000
1992	111000000
1993	113000000
1994	115000000
1995	119000000
1996	125000000
1997	130000000
1998	135000000
1999	140000000
2000	147000000
2001	151000000
2002	157000000
2003	160000000
2004	162000000
2005	161000000
2006	159000000
2007	156000000
2008	153000000
2009	150000000
2010	148000000
2011	145000000
2012	142000000
2013	142000000
2014	139000000
2015	138000000
2016	137000000
2017	136000000
2018	137000000