Year	Number
1970	78266968
1971	80986544
1972	80394416
1973	75231648
1974	74578184
1975	72185912
1976	71819952
1977	74198792
1978	80140160
1979	80599136
1980	78076744
1981	75572864
1982	74557480
1983	73960904
1984	72877408
1985	70020592
1986	66527756
1987	65323352
1988	63426728
1989	61552760
1990	63035508
1991	62666348
1992	63959940
1993	63964320
1994	64258012
1995	66442640
1996	67682808
1997	67902464
1998	65096000
1999	60666976
2000	57351840
2001	54873588
2002	52895388
2003	45056700
2004	42181704
2005	39083784
2006	37986588
2007	34008852
2008	32084156
2009	31859172
2010	32100000
2011	31400000
2012	30800000
2013	30400000
2014	30300000
2015	31400000
2016	31300000
2017	31700000
2018	32300000