Year	Percent
1991	25.518
1992	25.969
1993	26.61
1994	27.038
1995	26.176
1996	26.125
1997	25.295
1998	24.331
1999	23.418
2000	22.09
2001	21.969
2002	21.186
2003	20.508
2004	20.642
2005	20.594
2006	20.569
2007	20.495
2008	20.849
2009	20.155
2010	20.225
2011	19.853
2012	21.159
2013	21.918
2014	21.499
2015	21.02
2016	20.487
2017	20.48
2018	20.278
2019	20.1
2020	19.954
2021	19.833
2022	19.735