Year	Percent
1991	48.74
1992	47.8
1993	47.88
1994	48.08
1995	48.12
1996	46.86
1997	46.09
1998	45.9
1999	45.39
2000	45.11
2001	44.99
2002	41.86
2003	41.42
2004	40.9
2005	42.06
2006	42.21
2007	43.22
2008	43.38
2009	41.69
2010	40.55
2011	42.65
2012	42.39
2013	42.24
2014	42.32
2015	42.28
2016	41.93
2017	41.53
2018	41.35
2019	41.04