Year	Number
1975	4.32542684743845
1976	5.7303550480409315
1977	6.729940502534793
1978	8.90700507236851
1979	9.324408708938304
1980	9.656259954631102
1981	8.960878910300769
1982	8.556474587611742
1983	10.225308038230045
1984	8.185989960155913
1985	6.912887604181674
1986	4.58184234855549
1987	4.616509889162613
1988	2.7612089506306243
1989	3.7434086649294445
1990	3.546363977533736
1991	4.666058479401957
1992	2.6070911833279693
1993	2.2013957104836592
1994	2.8929737175478363
1995	2.1646207361110137
1996	2.301933773417208
1997	1.7893778583886204
1998	1.9991462795690378
1999	3.0146050089871554
2000	2.1083246449382482
2001	2.3005929131203375
2002	2.572561049442145
2003	3.084031436386657
2004	3.0240445381085115
2005	2.8439493956179946
2006	3.0477275199715197
2007	3.9048703716256203
2008	3.169160350377173
2009	5.380369629028357
2010	4.10936410793186
2011	4.127952889535318
2012	4.328231723131024
2013	4.682958239988757
2014	5.51761906093267
2015	5.3601597026856505
2016	6.512340004979971
2017	6.443572159456076
2018	5.679580964738714
2019	6.035936720353537
2020	8.962902536102098
2021	7.3222808340382635
2022	6.113157891988199
2023	6.040430224539838