Year	Percent
1991	31.405
1992	30.568
1993	30.738
1994	30.027
1995	30.198
1996	29.963
1997	29.045
1998	29.526
1999	28.941
2000	29.792
2001	29.504
2002	28.664
2003	30.098
2004	29.926
2005	28.707
2006	26.721
2007	26.136
2008	25.652
2009	24.807
2010	23.547
2011	23.308
2012	21.736
2013	23.159
2014	23.147
2015	18.085
2016	17.867
2017	17.766
2018	17.593
2019	17.458
2020	17.331
2021	17.214
2022	17.111