Year	Percent
1991	32.95
1992	32.93
1993	33.32
1994	34.82
1995	36.19
1996	36.61
1997	36.55
1998	36.46
1999	36.34
2000	36.27
2001	35.77
2002	35.18
2003	34.97
2004	34.91
2005	34.83
2006	34.96
2007	36.51
2008	36.42
2009	37.05
2010	36.57
2011	35.83
2012	35.37
2013	34.3
2014	34.59
2015	34.15
2016	33.34
2017	33.19
2018	33.02
2019	32.83
2020	30.88