Year	Number
1972	10.57618
1973	10.92968
1974	10.9991
1977	11.40379
1987	7.8173
1988	7.02836
1989	7.48577
1990	7.31765
1991	7.23346
1992	6.92296
1993	8.09795
1994	8.29635
2013	9.44806
2014	9.42359
2015	9.42496
2016	9.14736
2017	8.98821