Year	Number
1973	26454492
1974	26326180
1975	26159376
1976	26113290
1977	25414248
1978	24488006
1979	23270186
1980	23038608
1981	22929450
1982	23340474
1983	23689524
1984	24529892
1985	25910296
1986	27635168
1987	29459700
1988	30828680
1989	32549308
1990	33600892
1991	33829472
1992	35194888
1993	35691504
1994	36475052
1995	36850512
1996	39395392
1997	37910848
1998	38442040
1999	38726792
2000	37915788
2001	36751040
2002	34986464
2003	32463278
2004	31450690
2005	31138864
2006	30207918
2007	29026640
2008	29188364
2009	29306896
2010	30900000
2011	30400000
2012	30500000
2013	31400000
2014	31300000
2015	32400000
2016	32800000
2017	33700000
2018	34200000