Year	Percent
1991	22.117
1992	21.591
1993	22.22
1994	22.291
1995	22.17
1996	16.021
1997	15.849
1998	15.754
1999	15.622
2000	15.395
2001	15.486
2002	15.387
2003	15.163
2004	15.118
2005	15.738
2006	15.756
2007	16.228
2008	15.976
2009	15.914
2010	16.515
2011	14.928
2012	16.291
2013	16.358
2014	16.211
2015	16.112
2016	15.229
2017	15.154
2018	15.107
2019	15.06
2020	15.015
2021	14.969
2022	14.924