Year	Number
1972	10.638913902111815
1973	10.343753041040666
1974	9.090528896646976
1975	7.199076946064361
1976	5.304971910403839
1977	5.578711137552526
1978	6.3673860259581785
1979	6.803133248415798
1980	6.326428157007726
1981	4.202147972836392
1982	3.7848940932149238
1983	3.7316436144207454
1984	2.5481553783209843
1985	2.3663976854540127
1986	2.8841503464576133
1987	2.745001370201404
1988	1.2086740120470754
1989	2.906788346305881
1990	3.5490298816445383
1991	3.4235597526639925
1992	2.5842526839238924
1993	4.7649664190209
1994	5.0088559809034985
1995	5.163678953564882
1996	4.2302875255498575
1997	5.180320977250718
1998	4.235805845043451
1999	6.0771829315811745
2000	6.489678081582882
2001	5.844558856448542
2002	7.265802645489344
2003	8.715629020713935
2004	6.6817213410046605
2005	5.321950233181497
2006	6.067124149047117
2007	5.791324444035246
2008	5.386498643947488
2009	8.543931279020674
2010	8.45757169717942
2011	6.515514358160149
2012	4.40545435759904
2013	6.556657477950752
2014	7.3269809177961855
2015	8.304930886739744
2016	8.146294089939447