Year	Percent
1991	39.28
1992	40.83
1993	42.31
1994	43.76
1995	46.39
1996	47.46
1997	48.52
1998	50.07
1999	51.9
2000	48
2001	50.56
2002	55.45
2003	57.19
2004	59.3
2005	56.34
2006	59.67
2007	62.67
2008	63.25
2009	63.82
2010	64.95
2011	63.44
2012	63.35
2013	62.13
2014	60.12
2015	57.12
2016	55.7
2017	57.17
2018	57.59
2019	57.91