Year	Number
1970	12259
1971	11965
1972	10858
1973	11135
1974	10985
1975	10777
1976	10597
1977	10345
1978	10347
1979	10492
1980	9463
1981	9505
1982	10286
1983	9921
1984	10657
1985	10363
1986	10264
1987	10199
1988	9962
1989	9998
1990	10006
1991	9843
1992	10188
1993	10711
1994	10553
1995	10356
1996	10618
2007	14242
2008	14850
2009	16171
2014	14683
2015	14914
2016	15734
2017	15969
2018	16294
2019	16545
2020	16725
2021	16925