Year	Percent
1991	34.61
1992	35.17
1993	35.57
1994	35.53
1995	35.56
1996	35.53
1997	35.56
1998	35.62
1999	35.64
2000	35.71
2001	35.72
2002	35.69
2003	35.69
2004	35.74
2005	35.89
2006	36.07
2007	36.22
2008	36.34
2009	36.26
2010	36.36
2011	36.51
2012	36.65
2013	36.47
2014	36.35
2015	36.19
2016	36.15
2017	36.08
2018	35.94
2019	35.73