Year	Percent
1981	29.6
1982	29.6
1987	31.34
1989	31.77
1990	57.21
1991	53.36
1998	39.22
2000	37.74
2002	37.48
2003	42.84
2004	43.67
2006	43.96
2010	44.29
2011	42.58
2012	48.25
2013	50.96
2014	49.01
2015	49.23
2016	49.61