Year	Percent
1991	84.43
1992	83.67
1993	83.17
1994	82.57
1995	82.01
1996	81.5
1997	81.06
1998	80.58
1999	79.57
2000	78.26
2001	77.17
2002	75.96
2003	74.52
2004	73.06
2005	71.53
2006	70
2007	68.51
2008	67.15
2009	65.61
2010	64.23
2011	63.49
2012	62.51
2013	61.37
2014	60.32
2015	59.4
2016	54.39
2017	49.48
2018	48.27
2019	45.27