Year	Number
1970	30363756
1971	31299940
1972	30567776
1973	29551918
1974	30322964
1975	29529888
1976	29118764
1977	29053610
1978	29046226
1979	29194416
1980	28974920
1981	29147864
1982	30183658
1983	30669558
1984	31648516
1985	32875242
1986	33621104
1987	35011924
1988	34417272
1989	35685720
1990	37294824
1991	37240260
1992	38363300
1993	39385016
1994	39678364
1995	39381504
1996	39916044
1997	39050900
1998	39879212
1999	40807544
2000	39328240
2001	37911300
2002	35426360
2003	32945120
2004	31276496
2005	29200124
2006	27339568
2007	26444824
2008	24253960
2009	24293246
2010	25300000
2011	24400000
2012	24300000
2013	23800000
2014	23600000
2015	24500000
2016	25100000
2017	25800000
2018	26600000