Year	Percent
1973	22.86
1974	26.41
1975	26.41
1976	26.41
1977	26.41
1978	26.41
1979	26.77
1980	26.77
1981	26.77
1982	26.77
1983	27.54
1984	27.54
1985	28.69
1986	26.77
1987	29.55
1988	28.91
1989	28.91
1990	28.92
1991	32.66
1992	32.01
1993	33.49
1994	32.42
1995	34.62
1996	34.62
1997	36.88
1998	35.59
1999	35.59
2000	33.55
2001	33.55
2002	37.15
2003	37.15
2004	36.6
2005	36.6
2006	35.87
2007	35.37
2008	35.15
2009	35.71
2010	35.19
2011	34.74
2013	34.84
2014	34.89
2015	34.97
2016	34.14