Year	Number
1971	4081
1972	5178
1973	4773
1974	4872
1975	9910
1976	10197
1977	10088
1978	10077
1979	9797
1980	9413
1981	8626
1982	8645
1983	8578
1984	9994
1985	9694
1986	9571
1987	9669
1988	9600
1989	9319
1990	9406
1991	9776
1992	9896
1993	10213
2002	14467
2003	14860
2004	13660
2005	12549
2007	13060
2008	12469
2009	11031
2010	11500
2013	10040
2014	9736
2015	9309
2016	9185
2017	8834
2018	9135
2020	8856