Year	Number
1980	11866
1981	12192
1982	13184
1983	14273
1984	15148
1985	14989
1986	15894
1987	17468
1988	17786
1989	19679
1990	19791
1991	18743
1992	22654
1993	19811
1994	20151
1995	22899
1996	24642
1997	18727
1998	15624
1999	17609
2000	22003
2001	18491
2002	16361
2003	16375
2004	19550
2005	21130
2006	22513
2007	24348
2008	22176
2009	19141
2010	21013
2011	22343
2012	23718
2013	23636
2014	24574
2015	26906
2016	29672
2017	34029