Year	Number
1971	2953
1972	2915
1973	3564
1974	4349
1975	5494
1976	6441
1977	7547
1978	8826
1979	9266
1980	9880
1981	14001
1982	17242
1983	20549
1984	25310
1985	29026
1986	30789
1987	31493
1988	33533
1989	29235
1990	26525
1991	25038
1992	25499
1993	27435
1994	30052
1995	31485
1996	33108
1998	39701
1999	41821
2000	41534
2002	42481
2003	34855
2004	35502
2005	30949
2006	32330
2007	31432
2008	28185
2010	23829
2011	25076
2013	28873
2014	28257
2017	26597
2018	23181