Year	Number
1972	18.90909
1975	53.11111
1976	26.15789
1981	25.46667
1982	26
1983	25.51852
1984	28.61404
1985	25.8381
1986	26.24444
1987	26.70056
1988	27.82587
1989	31.0995
1990	25.52511
1991	28.25417
1992	29.77647
1993	29.41852
1994	28.37037
1995	28.68091
1996	35.94488
1997	40.20095
1998	40.91837
2007	23.59779
2011	23.30854
2012	23.55877
2013	24.66874
2015	22.30119
2016	17.2911
2017	17.58385
2018	17.21239