Year	Percent
1991	45.67
1992	45.07
1993	44.65
1994	45.93
1995	44.82
1996	42.54
1997	41.19
1998	44.9
1999	43.71
2000	42.31
2001	41.08
2002	40.7
2003	42.9
2004	41.63
2005	41.35
2006	42.48
2007	42.09
2008	41.94
2009	40.28
2010	39.3
2011	40.16
2012	40.85
2013	40.39
2014	38.9
2015	38.66
2016	39.23
2017	39.45
2018	39.43
2019	39.26