Year	Percent
1991	76.67
1992	75.93
1993	75.16
1994	74.4
1995	73.69
1996	72.94
1997	72.21
1998	71.47
1999	70.61
2000	69.77
2001	68.91
2002	67.99
2003	67.09
2004	65.7
2005	64.28
2006	63.72
2007	62.41
2008	60.49
2009	58.3
2010	56.21
2011	54.13
2012	52.04
2013	49.93
2014	47.9
2015	47.73
2016	47.6
2017	47.5
2018	47.39
2019	47.13