Year	Percent
1991	34.6
1992	34.81
1993	34.37
1994	34.36
1995	33.23
1996	32.54
1997	32.42
1998	31.95
1999	31.3
2000	30.14
2001	29.39
2002	28.97
2003	28.47
2004	27.84
2005	27.17
2006	27.03
2007	26.45
2008	26.21
2009	26.34
2010	26.15
2011	25.9
2012	25.83
2013	26.12
2014	26.31
2015	26.06
2016	25.73
2017	25.97
2018	26.35
2019	26.05