Year	Number
1974	18
1975	21
1976	40
1981	36
1982	24.07143
1983	27.03125
1984	23.56757
1985	20.28395
1986	23.4507
1987	21.54237
1988	21.48819
1989	22.02985
1990	21.94245
1991	20.34254
1992	20.70098
1993	19.88789
1994	19.86555
1995	18.69643
1996	19.64552
1997	19.03245
1998	20.14121
2009	19.4328
2013	25.68042
2014	27.98621
2015	25.2495
2016	24.91701
2017	22.56189
2018	20.77221