Year	Percent
1991	35.152
1992	36.413
1993	35.991
1994	34.439
1995	35.706
1996	33.005
1997	34.357
1998	33.096
1999	32.387
2000	31.755
2001	30.236
2002	25.557
2003	23.372
2004	25.579
2005	21.606
2006	20.733
2007	20.221
2008	20.035
2009	20.238
2010	20.067
2011	19.923
2012	19.751
2013	18.783
2014	18.198
2015	19.577
2016	17.234
2017	17.594
2018	17.634
2019	17.155
2020	17.195
2021	17.132
2022	16.989