Year	Percent
1991	29.569
1992	29.173
1993	28.969
1994	28.539
1995	28.117
1996	27.814
1997	27.419
1998	29.336
1999	28.912
2000	28.545
2001	29.551
2002	29.562
2003	29.364
2004	29.696
2005	30.025
2006	29.648
2007	30.409
2008	30.493
2009	29.41
2010	27.53
2011	24.617
2012	22.806
2013	21.066
2014	20.208
2015	19.885
2016	20.254
2017	20.387
2018	20.531
2019	20.611
2020	20.593
2021	20.568
2022	20.469