Year	Number
1975	1.9388796497665517
1976	1.6719113018327065
1977	1.475665605670589
1978	1.9939909129413844
1979	2.6293198850111232
1980	3.036705024921324
1981	3.101250681188311
1982	3.422701901611924
1983	3.54304371464694
1984	4.785020598739737
1985	6.600372471875067
1986	4.7617323220587116
1987	4.965680521627481
1988	4.250910811985334
1989	4.27683497123731
1990	4.163585077106119
1991	3.6829661164062175
1992	3.295404144489953
1993	5.745296137268631
1994	5.174503160379116
1995	5.167243232048053
1996	5.616452996597686
1997	4.809407478249377
1998	3.7709662485135262
1999	5.019530477794966
2000	5.647746170455178
2001	4.85481006981423
2002	6.183177484513244
2003	6.133359107199721
2004	5.913649109273902
2005	5.282149532042899
2006	5.425997326319829
2007	4.4819044672924235
2008	3.3647291862015525
2009	4.518837460928554
2010	4.250084383503181
2011	3.4301610172752555
2012	3.4852727154399883
2013	3.794434393479974
2014	4.316610973464967
2015	4.607918126447527
2016	4.892908175916538
2017	4.996740518406527
2018	4.377053769634493
2019	4.6884139603032295
2020	6.462796797297931
2021	5.705800788440848
2022	4.282834221167539
2023	4.7502776746404