Year	Percent
1990	28.78
1991	28.78
1992	28.82
1993	28.88
1994	28.92
1995	28.87
1996	28.85
1997	28.81
1998	28.76
1999	28.7
2000	28.63
2001	28.55
2002	28.47
2003	28.38
2004	28.28
2005	28.17
2006	28.31
2007	28.46
2008	28.62
2009	28.78
2010	28.95
2011	28.91
2012	28.86
2013	28.81
2014	28.02
2015	27.02
2016	29.72
2017	32.01
2018	31.94
2019	31.85