Year	Percent
1991	46.1
1992	46.01
1993	45.82
1994	45.79
1995	45.59
1996	45.48
1997	45.55
1998	45.49
1999	45.39
2000	45.42
2001	44.98
2002	44.5
2003	44.05
2004	43.65
2005	43.27
2006	42.94
2007	42.65
2008	42.34
2009	41.87
2010	41.54
2011	41.24
2012	40.94
2013	40.83
2014	40.77
2015	40.7
2016	40.63
2017	40.58
2018	40.72
2019	40.77
2020	39.81