Year	Percent
1991	25.44
1992	25.55
1993	25.898
1994	25.961
1995	25.162
1996	24.772
1997	23.685
1998	22.736
1999	21.459
2000	20.137
2001	19.972
2002	18.893
2003	18.152
2004	18.095
2005	18.053
2006	17.755
2007	17.545
2008	17.613
2009	16.876
2010	16.732
2011	16.444
2012	17.358
2013	17.915
2014	17.644
2015	17.326
2016	16.987
2017	16.961
2018	16.772
2019	16.615
2020	16.497
2021	16.395
2022	16.313