Year	Percent
1991	47.7
1992	45.25
1993	40.61
1994	43.9
1995	41.9
1996	42.82
1997	41.08
1998	40.24
1999	40.45
2000	37.64
2001	35.95
2002	33.78
2003	31.38
2004	31.34
2005	31.69
2006	31.76
2007	31.7
2008	31.91
2009	30.45
2010	31.63
2011	33.44
2012	32.68
2013	33.43
2014	34.43
2015	34.95
2016	34.87
2017	35.08
2018	35.69
2019	33.88