Year	Percent
1991	64.61
1992	64.58
1993	63.2
1994	62.11
1995	60.72
1996	59.2
1997	57.94
1998	52.37
1999	48.86
2000	49.31
2001	49.53
2002	49.29
2003	48.45
2004	49.61
2005	49.24
2006	46.58
2007	47.31
2008	46.57
2009	46.79
2010	45.11
2011	45.91
2012	45.34
2013	42.92
2014	41.12
2015	40.24
2016	39.62
2017	38.75
2018	39.77
2019	38.6