Year	Number
1981	10.776240542033513
1982	14.564133936089904
1983	17.730203546792485
1984	10.074392078591607
1985	9.694505497012344
1986	8.427882873088352
1987	7.591540399759048
1988	9.730769992518495
1989	7.5748931485309345
1990	8.397628728694517
1991	8.828231030628833
1992	6.561040093660066
1993	6.461067982952057
1994	6.36125314152181
1995	7.052972273180095
1996	7.58629279401516
1997	7.677885357972489
1998	6.6249240837324495
1999	6.6588819935167685
2000	9.063749136943391
2001	7.620497821989667
2002	6.8991667030998975
2003	7.668036547135988
2004	7.364604798269777
2005	8.620151409122139
2006	7.969602856922964
2007	8.204928464162398
2008	7.134985749468618
2009	6.056501198774094
2010	5.206431007194837
2011	3.9470243576470168
2012	4.097172310617556
2013	3.969768365986343
2014	4.054483629897907
2015	4.824227911913002
2016	4.321342033722726
2017	3.700413585825846
2018	3.6238414643669583
2019	3.0795550951066892
2020	2.74830594199918
2021	3.3106361278023044
2022	3.943256480811205
2023	3.97708903085742