Year	Percent
1991	48.66
1992	44.88
1993	43.8
1994	44.66
1995	46.53
1996	45.7
1997	49.19
1998	55.53
1999	59.56
2000	61.47
2001	59.39
2002	56.57
2003	57.06
2004	55.92
2005	61.03
2006	62.72
2007	62.39
2008	56.41
2009	44.92
2010	38.71
2011	36.39
2012	35.09
2013	36.77
2014	36.86
2015	37.73
2016	42.07
2017	40.16
2018	40.37
2019	41.12