Year	Percent
1991	42.56
1992	41.85
1993	41.14
1994	40.33
1995	39.33
1996	37.85
1997	36.88
1998	36.61
1999	41.79
2000	40.12
2001	38.4
2002	39.74
2003	40.6
2004	41.1
2005	41.17
2006	42.13
2007	41.21
2008	40.07
2009	38.94
2010	38.06
2011	37.47
2012	36.87
2013	36.74
2014	36.31
2015	35.96
2016	35.53
2017	36.27
2018	36.59
2019	36.39