Year	Percent
1991	42.51
1992	41.81
1993	40.67
1994	40.59
1995	40.37
1996	40.29
1997	39.79
1998	40.04
1999	39.27
2000	38.97
2001	38.73
2002	38.6
2003	38.13
2004	37.76
2005	37.49
2006	37.51
2007	37.4
2008	37.23
2009	35.99
2010	35.71
2011	37.39
2012	37.46
2013	38.08
2014	38.12
2015	36.84
2016	37.14
2017	37.08
2018	37.87
2019	37.62