Year	Number
1971	541718
1972	557525
1973	574774
1974	591325
1975	601262
1976	612297
1977	620968
1978	590588
1979	585347
1980	575922
1981	583382
1982	565276
1983	548838
1984	524067
1985	500702
1986	495755
1987	473467
1988	454848
1989	441184
1990	429976
1991	427286
1992	441996
1993	459011
1994	469915
1995	476273
1996	479820
1997	480966
1998	460370
1999	486779
2000	486937
2001	486054
2002	489936
2003	497517
2004	478230
2005	481324
2006	480298
2007	476624
2008	470889
2009	460934
2010	449729
2011	438879
2012	430657
2013	446948.53333
2014	443882.91667
2015	442411.33535
2016	445740.41972
2017	449201.08333