Year	Percent
1991	18.333
1992	18.275
1993	17.987
1994	17.538
1995	17.221
1996	16.97
1997	16.445
1998	15.991
1999	15.582
2000	15.011
2001	14.655
2002	14.451
2003	14.083
2004	13.765
2005	13.556
2006	13.247
2007	13.071
2008	13.164
2009	13.65
2010	13.625
2011	13.485
2012	13.48
2013	13.283
2014	13.019
2015	12.793
2016	12.613
2017	12.535
2018	12.406
2019	12.221
2020	11.998
2021	11.75
2022	11.506