Year	Percent
1990	36.51
1991	36.72
1992	36.84
1993	36.86
1994	36.86
1995	36.8
1996	36.88
1997	36.89
1998	36.89
1999	36.84
2000	36.78
2001	36.84
2002	36.79
2003	36.82
2004	36.76
2005	36.65
2006	36.6
2007	36.36
2008	36.17
2009	36.12
2010	35.85
2011	35.59
2012	35.3
2013	35.05
2014	34.8
2015	34.56
2016	34.07
2017	33.6
2018	33.25
2019	32.91