Year	Number
1970	19373
1972	16965
1973	15316
1975	17124
1976	14580
1978	16358
1979	18450
1980	18052
1981	16626
1982	19716
1985	25556
1986	25022
1987	25412
1989	26020
1990	27070
1991	26922
2011	1523
2012	1463
2013	3801
2014	7998
2015	7504
2016	7199