Year	Percent
1991	42.97
1992	42.81
1993	41.46
1994	39.88
1995	39.57
1996	37.25
1997	36.91
1998	34.86
1999	34.69
2000	35.52
2001	36.3
2002	36.97
2003	37.65
2004	38.24
2005	38.86
2006	39.5
2007	40.03
2008	40
2009	39.89
2010	39.64
2011	40.01
2012	40.14
2013	40.18
2014	40.03
2015	39.87
2016	39.77
2017	39.18
2018	39
2019	38.72