Year	Percent
1991	19.694
1992	19.935
1993	19.717
1994	19.8
1995	18.922
1996	18.27
1997	18.154
1998	17.803
1999	17.428
2000	16.598
2001	15.757
2002	15.848
2003	15.865
2004	15.811
2005	15.704
2006	15.987
2007	15.023
2008	14.399
2009	14.275
2010	13.731
2011	12.87
2012	12.527
2013	12.793
2014	12.903
2015	12.892
2016	12.591
2017	12.597
2018	12.516
2019	12.404
2020	12.285
2021	12.174
2022	12.031