Year	Number
1977	6.89583
1979	8.54902
1983	3.40625
1984	6.38947
1986	3.98013
1987	5.43103
1992	5.83193
1993	5.50758
1994	5.47687
1998	6.43929
1999	7.43976
2000	8.24845
2001	8.68023
2002	9.10928
2003	9.23984
2004	8.59615
2005	8.51356
2006	8.35082
2007	8.14176
2008	8.06763
2009	9.5721
2010	8.34682
2011	9.61684
2012	11.7574
2013	13.18891
2014	15.11647
2015	11.91447
2016	11.12121
2017	12.19033
2018	12.41771