Year	Number
1971	426045
1972	421276
1973	414047
1974	412301
1975	404698
1976	400282
1977	404966
1978	413893
1979	431761
1980	458187
1982	477986
1983	472914
1984	439199
1985	423882
1986	413106
1987	450427
1988	451916
1989	505448
1990	517846
1991	511056
1992	460412
1993	513136
1994	496433
1995	528961
1996	547534
1997	452039
1998	350267
1999	315952
2000	347320
2001	388548
2002	391928
2003	390658
2004	382065
2005	382571
2006	380933
2007	359952
2008	349300
2009	340560
2010	334690
2011	318506
2012	299908
2013	323681
2014	306155
2015	294696
2016	286502
2017	283313