Year	Percent
1991	29.21926
1992	29.08187
1993	28.88806
1994	28.67482
1995	28.5306
1996	28.20359
1997	27.90152
1998	27.55281
1999	27.06599
2000	26.539
2001	26.03935
2002	25.50638
2003	24.88235
2004	24.31105
2005	23.63363
2006	23.0205
2007	22.39571
2008	21.74069
2009	21.05418
2010	20.54897
2011	20.43692
2012	20.02242
2013	19.62343
2014	19.22548
2015	18.75886
2016	18.23678
2017	17.57979
2018	16.9606
2019	16.4084