Year	%
2000	3.6386393224327067
2001	3.562769504816715
2002	3.4478768584993165
2003	3.3426998553453853
2004	3.273052575036537
2005	3.168065055368742
2006	3.096053888496264
2007	3.0867020355562955
2008	3.095103870028247
2009	3.079498830246132
2010	3.0745038100772604
2011	2.917958681552312
2012	2.9126251173446227
2013	2.9152369166011933
2014	2.926863552327091
2015	2.7938286784185546
2016	2.8030092435362186
2017	2.746519270101354
2018	2.733283174833429
2019	2.6795708575760853
2020	2.4829370674241735