Year	Percent
1991	44.35
1992	44.6
1993	44.51
1994	44.66
1995	44.22
1996	44.04
1997	44.16
1998	44.12
1999	43.98
2000	43.57
2001	43.18
2002	43.01
2003	42.8
2004	42.54
2005	42.25
2006	42.13
2007	41.76
2008	41.62
2009	41.67
2010	41.55
2011	41.42
2012	40.42
2013	40.57
2014	40.73
2015	40.65
2016	40.27
2017	40.25
2018	40.35
2019	40.13
2020	39.2