Year	Percent
1991	25.01
1992	24.92
1993	24.782
1994	24.684
1995	24.47
1996	24.257
1997	24.048
1998	23.759
1999	23.454
2000	23.205
2001	22.697
2002	22.193
2003	21.65
2004	21.136
2005	20.614
2006	20.153
2007	19.736
2008	19.291
2009	18.851
2010	18.387
2011	17.969
2012	17.549
2013	17.376
2014	17.196
2015	17.016
2016	16.891
2017	16.695
2018	16.497
2019	16.309
2020	16.138
2021	15.965
2022	15.784