Year	Percent
1991	17.618
1992	18.871
1993	20.035
1994	20.485
1995	17.299
1996	17.365
1997	16.482
1998	15.714
1999	16.084
2000	15.903
2001	15.217
2002	15.325
2003	14.987
2004	15.057
2005	15.352
2006	15.178
2007	14.923
2008	14.455
2009	14.764
2010	14.985
2011	14.406
2012	14.572
2013	14.574
2014	14.103
2015	13.953
2016	13.565
2017	13.542
2018	13.459
2019	13.424
2020	13.396
2021	13.368
2022	13.339