Year	Number
1980	4773
1981	6463
1982	7299
1983	8365
1984	8840
1985	7107
1986	7585
1987	8587
1988	10480
1989	12914
1990	13262
1991	13144
1992	11961
1993	13034
1994	16262
1995	16634
1996	18621
1997	20843
1998	14492
1999	16070
2000	19477
2001	20729
2002	17862
2003	18746
2004	21878
2005	22697
2006	23783
2007	28115
2008	28394
2009	24946
2010	21776
2011	19928
2012	21497
2013	21906
2014	22264
2015	22978
2016	24775
2017	24647