Year	Number
1970	72616064
1971	74971096
1972	74442432
1973	68150872
1974	66714088
1975	64391684
1976	64005300
1977	66886476
1978	74683992
1979	75476352
1980	73217624
1981	69960976
1982	68529448
1983	66830744
1984	64018172
1985	58734084
1986	52649128
1987	49970080
1988	46866788
1989	42431080
1990	43559744
1991	42816408
1992	43925800
1993	43792380
1994	44488120
1995	48039620
1996	49130160
1997	51811692
1998	47341292
1999	40226316
2000	36997812
2001	34775604
2002	33577352
2003	26797308
2004	24682548
2005	21771698
2006	20886382
2007	15756803
2008	14235018
2009	15426801
2010	14900000
2011	15600000
2012	13900000
2013	13400000
2014	13300000
2015	12800000
2016	13000000
2017	12700000
2018	13400000