Year	Number
1970	31700520
1971	32657288
1972	31966536
1973	30945380
1974	31791014
1975	31068312
1976	30650926
1977	30616784
1978	30660556
1979	30805992
1980	30593836
1981	30665032
1982	31622230
1983	32141604
1984	33174080
1985	34330628
1986	35206080
1987	36577560
1988	36047072
1989	37316384
1990	38994612
1991	38783360
1992	39866320
1993	41003200
1994	41240800
1995	41034532
1996	41642272
1997	40762068
1998	41585208
1999	42539280
2000	40897480
2001	39555372
2002	36941980
2003	34655528
2004	33016068
2005	31023264
2006	29208672
2007	28052656
2008	25781978
2009	25841208
2010	26600000
2011	25400000
2012	25200000
2013	25200000
2014	25000000
2015	25600000
2016	25900000
2017	26000000
2018	26700000