Year	Percent
1991	42.32
1992	42.49
1993	42.39
1994	42.07
1995	41.76
1996	41.33
1997	41
1998	41.36
1999	41.23
2000	40.96
2001	40.86
2002	40.21
2003	39.59
2004	40.12
2005	40.01
2006	39.55
2007	39.5
2008	38.69
2009	38.82
2010	38.44
2011	39.84
2012	39.55
2013	39.03
2014	39.46
2015	38.32
2016	38.15
2017	35.42
2018	34.81
2019	34.08