Year	Percent
1991	6.472
1992	6.408
1993	6.194
1994	5.758
1995	5.151
1996	5.056
1997	4.712
1998	4.444
1999	4.108
2000	3.867
2001	3.651
2002	3.794
2003	3.659
2004	3.548
2005	3.609
2006	3.533
2007	3.588
2008	3.661
2009	3.651
2010	3.75
2011	3.751
2012	3.366
2013	3.292
2014	3.526
2015	3.548
2016	3.5
2017	3.543
2018	3.528
2019	3.52
2020	3.502
2021	3.494
2022	3.485