Year	Number
1980	2404
1981	2438
1986	2888
1987	1862
1988	3452
1989	1749
1990	5962
1991	4311
1992	4703
1993	6573
1994	14199
1995	11420
1996	10584
1997	9688
1998	10998
1999	10054
2000	10037
2001	10093
2002	10028
2003	10433
2004	12108
2005	13817
2006	13421
2007	12605
2008	15524
2009	14517
2010	16195
2013	20110
2014	25389
2015	17523
2016	15890
2017	14551