Year	Number
1967	1.1921966230602805
1968	1.7651330315635723
1969	1.2104701952768964
1970	1.3440504320219349
1971	1.4419703783947175
1972	1.8819475164675754
1973	1.8846212935077786
1974	2.0506757825541273
1975	1.8907645948201908
1976	1.217673915034719
1977	1.405789452652625
1978	1.9452984909825715
1979	1.6495376470040695
1980	1.5590005856514328
1981	1.79220028091903
1982	2.184044044284592
1983	2.0190248033592706
1984	2.0338654801558125
1985	2.275952084172562
1986	2.3979821510954817
1987	2.4408543265937834
1988	2.1346787342259206
1989	1.5151360507861036
1990	1.5195563519685897
1991	1.1537603795837605
1992	2.2923407084797325
1993	2.159932285155354
1994	2.622226632185581
1995	2.400729591843544
1996	2.921457958874803
1997	2.3520871927398512
1998	3.096476048792226
1999	2.3853389772506564
2000	3.453983022270824
2001	5.292717831024122
2002	4.99923383346712
2003	4.888643151686021
2004	3.401019971607981
2005	3.09234471666715
2006	2.9374241600997166
2007	3.7271229326448867
2008	3.0852516433321093
2009	4.191033006605478
2010	3.95630233742589
2011	3.611198563066467
2012	3.6877411682210375
2013	2.814049691383464
2014	2.4626289369034575
2015	2.419158613544688
2016	1.6834400560225982
2017	1.2564051086618868