Year	Number
1975	31551048
1976	31795740
1977	31290458
1978	30816382
1979	29905582
1980	29322792
1981	28799172
1982	28721932
1983	29300858
1984	30601426
1985	32338896
1986	34463028
1987	36513020
1988	38256984
1989	38922512
1990	40582600
1991	40837332
1992	42185244
1993	42936740
1994	43744472
1995	44024192
1996	46122496
1997	44443140
1998	44671916
1999	44763700
2000	43134820
2001	41684800
2002	40597668
2003	38573956
2004	37383808
2005	35569092
2006	34105056
2007	31784882
2008	31253968
2009	31393568
2010	33300000
2011	32000000
2012	31900000
2013	31900000
2014	32100000
2015	33000000
2016	33600000
2017	34200000
2018	34700000