Year	Percent
1991	43.06
1992	42.25
1993	41.95
1994	41.34
1995	41.12
1996	40.61
1997	39.55
1998	38.55
1999	37.57
2000	36.76
2001	36.01
2002	35.27
2003	34.62
2004	33.94
2005	33.23
2006	33.44
2007	33.49
2008	33.4
2009	33.12
2010	33.06
2011	33.09
2012	32.87
2013	32.75
2014	32.68
2015	33.4
2016	33.91
2017	33.31
2018	32.88
2019	32.74