Year	Number
1971	1914
1972	2182
1973	2013
1974	2463
1975	2788
1976	3060
1977	3123
1979	3617
1980	4584
1981	4119
1982	6125
1983	4987
1984	4492
1985	4474
1986	4627
1987	4645
1988	4936
1989	5884
1990	6789
1991	7202
1992	8372
1993	8729
1999	13109
2000	15188
2001	17396
2003	18421
2004	20376
2005	22432
2006	23002
2007	24577
2008	25610
2009	25877
2010	26403
2011	25877
2012	27381
2013	29730
2014	28232
2015	29989
2016	30030
2017	29957
2018	28566