Year	Percent
1990	35.52
1991	35.01
1992	34.63
1993	34.26
1994	33.79
1995	33.17
1996	32.67
1997	32.04
1998	31.61
1999	33.68
2000	36.48
2001	35.91
2002	35.31
2003	34.69
2004	34.07
2005	33.46
2006	33.02
2007	32.4
2008	31.76
2009	31.11
2010	30.4
2011	32.29
2012	34.22
2013	36.17
2014	36.1
2015	36.19
2016	35.96
2017	35.73
2018	35.41
2019	35.11