Year	Percent
1991	17.288
1992	17.884
1993	17.937
1994	17.743
1995	17.964
1996	18.012
1997	17.241
1998	17.395
1999	17.294
2000	16.071
2001	15.246
2002	15.465
2003	15.184
2004	14.735
2005	15.265
2006	15.113
2007	14.862
2008	14.263
2009	14.837
2010	14.399
2011	14.338
2012	14.381
2013	15.114
2014	14.646
2015	15.213
2016	14.874
2017	14.909
2018	14.829
2019	14.746
2020	14.672
2021	14.594
2022	14.517