Year	Percent
1991	3.752
1992	3.844
1993	3.483
1994	3.564
1995	3.554
1996	3.455
1997	3.473
1998	3.527
1999	3.479
2000	3.355
2001	3.566
2002	3.852
2003	3.762
2004	3.992
2005	4.203
2006	4.089
2007	4.101
2008	4.069
2009	4.158
2010	4.111
2011	4.135
2012	4.243
2013	4.352
2014	4.522
2015	4.471
2016	4.563
2017	4.538
2018	4.639
2019	4.732
2020	4.802
2021	4.847
2022	4.892