Year	Number
1992	6.334084817
1993	5.6186384897
1994	4.9031921625
1995	4.8056491945
1996	4.7081062264
1997	4.6105632584
1998	4.5130202904
1999	4.4154773223
2000	4.8268778876
2001	4.2100041655
2002	4.1824462329
2003	4.1548883003
2004	4.1273303677
2005	4.4071493757
2006	4.0722145025
2007	4.0446565699
2008	4.0170986373
2009	3.9895407047
2010	4.4325874673
2011	3.9344248394
2012	4.0700946615
2013	3.8793089742
2014	4.5031781716
2015	3.9708861041
2016	4.1203348925
2017	4.0961687054
2018	4.1222427493
2019	4.1222427493
2020	4.1222427493