Year	Percent
1990	27.65
1991	27.59
1992	27.67
1993	27.85
1994	28.09
1995	28.33
1996	28.37
1997	28.55
1998	28.56
1999	28.22
2000	28.37
2001	28.44
2002	27.99
2003	28.38
2004	27.38
2005	26.5
2006	25.16
2007	23.85
2008	23.92
2009	26.62
2010	27.84
2011	28.4
2012	29.19
2013	29.21
2014	29.56
2015	29.62
2016	29.93
2017	29.83
2018	28.92
2019	28.29