Year	Number
1971	9.4381
1973	8.03988
1977	5.52439
1979	3.50467
1980	3.29508
1981	3.33333
1982	3.9195
1985	4.3565
1987	6.34511
1992	6.38889
1993	5.98632
1994	7.35774
1995	9.28531
1996	7.80656
2004	8.84579
2005	9.40445
2006	14.17475
2007	19.2819
2008	28.75648
2009	17.86148
2010	16.24433
2011	13.6852
2012	14.33955
2013	12.15714
2014	15.22838
2017	14.09547
2018	15.16804