Year	Number
1967	3.295236464378812
1968	3.163414544771257
1969	2.4306789451354134
1970	2.631911225783346
1971	2.6944229635934747
1972	3.627779923550033
1973	4.345882642474109
1974	4.42212854669181
1975	3.5037252053729895
1976	3.1703273952385316
1977	3.2531698047004025
1978	3.2197944854837264
1979	4.3261688508597755
1980	4.558985835826846
1981	3.656609177342765
1982	4.3257419764286835
1983	4.068429065639897
1984	3.4372630313365726
1985	3.6672496017785625
1986	3.456464956275686
1987	3.786835784665312
1988	3.1231359274264774
1989	2.9325414443716844
1990	2.4472546523995264
1991	2.312859647773233
1992	2.3744730461061994
1993	3.163114525165596
1994	3.1073621745082307
1995	2.371250369197754
1996	1.9505011602007007
1997	1.6453710852687586
1998	1.46526639769799
1999	0.8675760874987718
2000	0.7603405348196975
2001	0.7383329229040103
2002	0.8031596632419572
2003	0.7528635894961341
2004	0.5020982565568106
2005	0.41817626363998833
2006	0.4312900488712897
2007	0.37512404331678184
2008	0.3713688124898301
2009	0.6364987673133115
2010	0.6748132148326084
2011	0.6479148997400475
2012	0.7506314886275186
2013	0.6087987065311576
2014	0.530212945603458
2015	0.524651765260603
2016	0.5063696445373854
2017	0.5047468176116723
2018	0.4434914807428637
2019	0.527284596953436
2020	0.7285533348520223
2021	0.7428933999331555
2022	0.6492915344937045
2023	0.6794396054591768