Year	Percent
1991	36.69608
1992	35.51082
1993	33.2044
1994	32.23119
1995	31.72624
1996	31.44931
1997	31.17855
1998	32.19328
1999	33.51601
2000	33.11572
2001	35.26814
2002	37.95838
2003	34.7272
2004	31.83071
2005	32.12756
2006	30.69432
2007	29.09959
2008	27.17696
2009	29.24629
2010	27.22549
2011	26.46135
2012	27.39349
2013	25.72271
2014	26.02545
2015	26.74197
2016	27.50882
2017	26.98243