Year	Percent
1991	47.07
1992	47.94
1993	49.95
1994	49.78
1995	49.38
1996	46.12
1997	45.67
1998	42.5
1999	37
2000	36.4
2001	41.47
2002	41.16
2003	42.41
2004	40.32
2005	40.62
2006	39.59
2007	38.5
2008	38.19
2009	40.54
2010	41.94
2011	43.47
2012	45.37
2013	45.04
2014	45.36
2015	46.03
2016	44.59
2017	43.69
2018	42.89
2019	40.72