Year	Percent
1991	26.64
1992	27.34
1993	28.03
1994	28.3
1995	28.04
1996	27.79
1997	27.78
1998	27.66
1999	27.67
2000	27.53
2001	27.39
2002	27.37
2003	27.41
2004	27.41
2005	27.6
2006	28.08
2007	28.59
2008	29.23
2009	30.17
2010	30
2011	29.15
2012	28.1
2013	27.24
2014	26.73
2015	26.66
2016	26.68
2017	27.08
2018	27.67
2019	28.17