Year	Number
1975	4.585696149931524
1976	4.126229568044416
1977	4.416847014999818
1978	5.24209612925692
1979	6.320410759135451
1980	5.720605105579189
1981	4.464924576079841
1982	4.8837950081989385
1983	4.788197721948076
1984	4.299838777894208
1985	4.407984399684997
1986	4.380652757450164
1987	4.86941530819623
1988	3.989549259681964
1989	4.015885389967464
1990	3.735131981842592
1991	3.8577119574317598
1992	3.0713564853714264
1993	3.3682744794958874
1994	3.437706339054946
1995	3.0527345826055794
1996	3.1460113565899848
1997	3.1484386502731554
1998	2.8433004524679215
1999	2.64791462822957
2000	2.3279787767384486
2001	2.2821327994937435
2002	2.756736984907201
2003	2.669405180667139
2004	2.360423778422034
2005	2.177222332377871
2006	2.131248799831951
2007	2.102755751768251
2008	1.847757718300722
2009	3.122371039600971
2010	3.0598997287826495
2011	2.7383714565637542
2012	3.1047373637840896
2013	2.982251968113999
2014	2.6424687952297115
2015	2.8610402526079843
2016	3.155782303639505
2017	3.6477568830372866
2018	3.18935240878934
2019	3.3886657126742215
2020	4.368133493957586
2021	3.636054906806267
2022	3.0240807284784372
2023	3.2024214911646474