Year	Percent
1991	17.38
1992	17.275
1993	16.503
1994	16.599
1995	15.991
1996	15.803
1997	15.548
1998	15.161
1999	14.85
2000	13.999
2001	13.347
2002	13.345
2003	14.402
2004	13.85
2005	13.91
2006	14.536
2007	14.212
2008	13.459
2009	14.261
2010	15.036
2011	15.143
2012	14.917
2013	14.562
2014	14.823
2015	14.772
2016	14.987
2017	14.836
2018	14.776
2019	14.723
2020	14.672
2021	14.624
2022	14.583