Year	Percent
1991	78.09
1992	76.81
1993	75.44
1994	74.08
1995	72.75
1996	71.44
1997	70.08
1998	68.65
1999	67.51
2000	66.42
2001	65.38
2002	64.3
2003	63.25
2004	62.25
2005	61.28
2006	60.37
2007	59.48
2008	58.56
2009	57.51
2010	56.57
2011	55.64
2012	54.7
2013	53.73
2014	52.74
2015	52.83
2016	52.81
2017	52.66
2018	52.4
2019	52.06