Year	Percent
1991	36.74
1992	36.62
1993	36.6
1994	36.67
1995	36.62
1996	36.76
1997	36.49
1998	36.16
1999	36
2000	36.46
2001	29.11
2002	26.33
2003	30.1
2004	29.56
2005	31.08
2006	31.38
2007	32.57
2008	30.16
2009	31.13
2010	31.04
2011	33.64
2012	33.27
2013	33.1
2014	33.15
2015	33.62
2016	33.17
2017	32.69
2018	32.1
2019	33.14
2020	31.07