Year	Percent
1982	29.31
1983	29.18
1984	30.92
1990	31.62
1991	32.65
1992	32.13
1993	29.54
1994	28.46
1995	26.99
1996	24.89
1997	25.41
1998	24.8
1999	23.6
2000	22.68
2001	21.94
2002	20.16
2003	21.65
2004	22.64
2005	23.21
2006	23.63
2008	23.88
2009	23.07
2010	23.9
2011	24.92
2012	23.9
2013	24.08
2014	24.55
2017	22.38