Year	Percent
1991	20.038
1992	20.183
1993	20.481
1994	20.288
1995	20.058
1996	19.974
1997	20.177
1998	19.959
1999	19.67
2000	20.036
2001	20.26
2002	20.399
2003	19.928
2004	19.715
2005	19.709
2006	19.015
2007	18.361
2008	18.243
2009	18.292
2010	18.422
2011	17.842
2012	17.225
2013	16.888
2014	17.193
2015	17.105
2016	17.111
2017	16.781
2018	16.847
2019	16.787
2020	16.677
2021	16.541
2022	16.397