Year	Number
1970	3931354
1971	4041309
1972	4664747
1973	5050721
1974	5426357
1975	6068065
1976	6706185
1977	7310619
1978	8231381
1979	8744413
1980	9216631
1981	9616325
1982	10100000
1983	10600000
1984	11200000
1985	11800000
1986	12600000
1987	13300000
1988	13900000
1989	14400000
1990	16100000
1991	16500000
1992	17000000
1993	17800000
1994	19200000
1995	20100000
1996	20800000
1997	22000000
1998	23100000
1999	24200000
2000	25000000
2001	25500000
2002	26000000
2003	26900000
2004	27200000
2005	27100000
2006	27100000
2007	27000000
2008	27200000
2009	27500000
2010	27400000
2011	28200000
2012	28100000
2013	26000000
2014	25600000
2015	25800000
2016	26100000
2017	26300000
2018	26700000