Year	Number
1970	49265068
1971	50067972
1972	49485136
1973	46989904
1974	46821156
1975	46081184
1976	45358288
1977	45001320
1978	46593584
1979	46008960
1980	43928352
1981	42695268
1982	42204364
1983	42146660
1984	42331260
1985	41843276
1986	41026728
1987	40936032
1988	39810280
1989	38922644
1990	40615496
1991	40489556
1992	41767096
1993	42818628
1994	44099416
1995	45852564
1996	48052748
1997	48992976
1998	47054652
1999	44588816
2000	42317580
2001	40772736
2002	39558944
2003	37384640
2004	34952304
2005	32236412
2006	32134556
2007	27606658
2008	27639980
2009	28976368
2010	29700000
2011	30200000
2012	28500000
2013	27800000
2014	27200000
2015	27400000
2016	26700000
2017	26800000
2018	26800000