Year	Number
1977	6.017064440764862
1978	5.932261889200097
1979	6.137593978958914
1980	4.285997069280581
1981	1.9584136482445362
1982	2.3734292889987394
1983	3.365124677350183
1984	3.133584903541292
1985	3.8841043024771835
1986	5.243618211281735
1987	3.5997329484635636
1988	2.572803920546927
1989	3.0324382308237663
1990	2.140573879603609
1991	4.812969026911342
1992	3.156868243308514
1993	3.617677027697671
1994	3.3441922166922486
1995	2.389841207377335
1996	2.985139872599452
1997	3.124941616646227
1998	3.1495579596499157
1999	2.8355734803506145
2000	3.6170223422047405
2001	4.362671268626447
2002	3.8819020290868345
2003	4.500642354302848
2004	3.946064378642749
2005	3.813170339574424
2006	3.5192114267731496
2007	3.2541850500265035
2008	3.449535788667357
2009	4.668473776303632
2010	4.532060746997644
2011	3.960173357883362
2012	4.1454045321719475
2013	4.302348507080753
2014	4.136070029610391
2015	4.4865595942514895
2016	5.392527746605767
2017	6.410206978035755
2018	6.404798898332965
2019	7.4103673669698065
2020	10.217361376776566
2021	8.239436857013608
2022	6.5425940002139855
2023	6.961389238779033