Year	Percent
1991	26.26
1992	26.06
1993	25.81
1994	25.69
1995	25.67
1996	25.78
1997	25.97
1998	26.17
1999	26.33
2000	26.49
2001	26.79
2002	27.01
2003	27.21
2004	27.39
2005	27.56
2006	27.69
2007	27.8
2008	27.86
2009	27.68
2010	27.66
2011	27.67
2012	27.72
2013	27.74
2014	27.81
2015	27.84
2016	27.85
2017	27.9
2018	27.94
2019	27.96