Year	Percent
1990	36.96
1991	36.93
1992	36.9
1993	36.84
1994	36.76
1995	36.63
1996	36.56
1997	35.86
1998	35.16
1999	34.46
2000	33.77
2001	33.3
2002	32.86
2003	32.45
2004	32.07
2005	31.71
2006	32.78
2007	33.88
2008	35.04
2009	36.25
2010	37.52
2011	38.89
2012	33.74
2013	28.96
2014	24.58
2015	25.29
2016	26.09
2017	26.03
2018	25.97
2019	25.92