Year	Number
1970	993804.1
1971	1059466
1972	1221865
1973	1406166
1974	1635313
1975	1868635
1976	2058853
1977	2123558
1978	2255210
1979	2401473
1980	2692919
1981	3125229
1982	3100908
1983	3361761
1984	4566646
1985	5450461
1986	6480836
1987	7276711
1988	7761343
1989	8147332
1990	8442839
1991	8722271
1992	9091956
1993	9653189
1994	10500000
1995	11700000
1996	12900000
1997	13800000
1998	14800000
1999	15900000
2000	15500000
2001	15700000
2002	15200000
2003	14600000
2004	16100000
2005	17100000
2006	18900000
2007	21100000
2008	23100000
2009	24300000
2010	25100000
2011	25400000
2012	25200000
2013	26700000
2014	25000000
2015	23100000
2016	22300000
2017	22700000
2018	22900000