Year	Percent
1991	28.787
1992	27.233
1993	27.119
1994	25.811
1995	25.664
1996	25.254
1997	24.057
1998	24.423
1999	23.678
2000	24.516
2001	23.958
2002	23.332
2003	24.036
2004	24.018
2005	23.496
2006	21.726
2007	20.571
2008	20.089
2009	20.008
2010	18.78
2011	18.206
2012	16.867
2013	17.854
2014	18.171
2015	15.096
2016	14.447
2017	14.366
2018	14.203
2019	14.083
2020	13.973
2021	13.875
2022	13.791