Year	Number
1971	17.95726
1972	34.82667
1977	26.45745
1978	28.67
1979	26.81308
1981	21.73913
1982	22.35897
1983	21.54962
1984	18.6
1987	22.4863
1988	23.89333
1999	15.25481
2002	14.98565
2003	14.79386
2004	14.80702
2005	10.30303
2007	13.96341
2008	14.93333
2009	10.5389
2010	14.47967
2013	13.50741
2014	12.13043
2015	11.76471
2016	11.65232
2017	12.24749
2018	12.36789