Year	Percent
1991	6.013
1992	5.818
1993	5.414
1994	5.286
1995	5.174
1996	5.012
1997	4.922
1998	4.836
1999	4.847
2000	4.775
2001	4.662
2002	4.555
2003	4.536
2004	4.47
2005	4.435
2006	4.326
2007	4.261
2008	4.268
2009	4.308
2010	4.213
2011	4.138
2012	4.105
2013	4.014
2014	3.979
2015	3.941
2016	3.849
2017	3.848
2018	3.776
2019	3.729
2020	3.713
2021	3.664
2022	3.615