Year	Percent
1982	34.93
1983	32.07
1984	32.63
1985	19.98
1988	21.1
1989	20.99
1990	20.67
1991	20.16
1992	21.56
1993	22.64
1994	22.64
1995	22.26
1996	22.9
1997	24.12
1998	23.61
1999	22.76
2006	26.77
2007	26.75
2009	25.3
2010	26.22
2011	26.46
2012	26.03
2013	26.39
2014	27.86
2015	27.23
2016	26.78
2017	26.54