Year	Number
1971	7506
1972	8143
1973	8937
1974	9631
1975	6921
1976	7461
1977	7409
1978	7466
1979	7576
1980	7135
1981	18450
1982	18738
1983	18686
1986	17705
1987	17099
1988	14790
1992	12397
1993	13183
1994	14153
1995	16595
1996	18129
1997	19333
1998	20084
1999	10622
2000	10853
2001	11172
2002	11313
2003	11558
2004	11369
2005	11335
2006	11553
2007	11843
2008	12043
2010	12867
2011	13245
2012	13525
2013	14612
2014	14892
2015	15566
2016	15821
2017	16067