Year	Number
1970	73448456
1971	76170776
1972	75634920
1973	70668440
1974	69966816
1975	67719792
1976	67641232
1977	70237064
1978	76319216
1979	76876808
1980	75157192
1981	72652104
1982	71846848
1983	71060808
1984	69819024
1985	67003472
1986	63800228
1987	62958136
1988	61258996
1989	59511664
1990	60935420
1991	60526048
1992	61633552
1993	61634368
1994	61893852
1995	64206956
1996	65479584
1997	65610512
1998	63506272
1999	59251736
2000	55900432
2001	53599896
2002	51424584
2003	43663448
2004	40907616
2005	38100760
2006	37124128
2007	33285404
2008	31417664
2009	31132792
2010	31300000
2011	30500000
2012	30100000
2013	29700000
2014	29700000
2015	30800000
2016	30900000
2017	31200000
2018	31700000