Year	Percent
1990	44.31
1991	43.8
1992	43.3
1993	42.8
1994	42.29
1995	41.79
1996	41.28
1997	40.78
1998	40.28
1999	39.77
2000	39.27
2001	38.76
2002	38.26
2003	37.76
2004	37.25
2005	36.75
2006	36.35
2007	35.94
2008	35.54
2009	35.14
2010	34.73
2011	34.39
2012	34.05
2013	33.71
2014	33.37
2015	33.03