Year	Percent
1990	31.78
1991	31.79
1992	31.88
1993	31.94
1994	31.99
1995	32.05
1996	32.11
1997	32.2
1998	32.27
1999	32.34
2000	32.39
2001	32.47
2002	32.56
2003	32.63
2004	32.68
2005	32.75
2006	32.81
2007	32.82
2008	32.84
2009	32.74
2010	30.16
2011	30.72
2012	31.88
2013	30.88
2014	29.96
2015	30.23
2016	29.82
2017	28.29
2018	28.38
2019	28.38