Year	Percent
1991	22.157
1992	20.856
1993	21.934
1994	22.036
1995	21.764
1996	21.816
1997	21.515
1998	21.528
1999	21.316
2000	21.006
2001	21.859
2002	21.074
2003	19.563
2004	19.464
2005	19.364
2006	18.15
2007	18.25
2008	17.869
2009	18.641
2010	18.641
2011	17.741
2012	18.241
2013	18.097
2014	17.973
2015	17.944
2016	17.838
2017	17.838
2018	17.83
2019	17.819
2020	17.804
2021	17.783
2022	17.763