Year	Percent
1991	38.89
1992	38.2
1993	37.78
1994	37.52
1995	37.39
1996	37.38
1997	37.41
1998	37.51
1999	37.5
2000	37.49
2001	37.39
2002	37.14
2003	37.09
2004	37
2005	36.91
2006	37.15
2007	36.79
2008	36.27
2009	35.42
2010	34.93
2011	34.88
2012	35.09
2013	35.43
2014	35.79
2015	35.98
2016	36.1
2017	36.17
2018	36.14
2019	35.69