Year	Percent
1991	35.35
1992	33.72
1993	33.08
1994	32.54
1995	30.67
1996	32.11
1997	33.24
1998	32.36
1999	31.44
2000	30.61
2001	31.49
2002	31.93
2003	32.71
2004	35.16
2005	36.04
2006	37.2
2007	36.45
2008	37.4
2009	37.82
2010	38.12
2011	38.25
2012	37.97
2013	39.37
2014	37.26
2015	37.24
2016	38.06
2017	37.66
2018	37.61
2019	37.51
2020	35.13