Year	Number
1970	18367238
1971	19276906
1972	18974756
1973	18331948
1974	18744952
1975	18164302
1976	17869842
1977	17930878
1978	17943246
1979	17910652
1980	17676682
1981	17576188
1982	18182844
1983	18558808
1984	18797880
1985	19421872
1986	19815882
1987	20548284
1988	20022794
1989	20619098
1990	21456112
1991	21248326
1992	21766392
1993	22347600
1994	22448820
1995	22652600
1996	22995596
1997	22541702
1998	22860236
1999	23135912
2000	22312080
2001	21619064
2002	20205820
2003	19012120
2004	18110384
2005	17183816
2006	16130580
2007	15410561
2008	14334257
2009	14223743
2010	14400000
2011	13700000
2012	13400000
2013	13400000
2014	13200000
2015	13600000
2016	13800000
2017	14000000
2018	14400000