Year	Percent
1981	96.06918
1982	72.42051
1983	64.02382
1984	53.75735
1985	58.32102
1986	49.74317
1987	62.32167
1988	65.4068
1989	59.29661
1990	57.54289
1991	48.49458
1992	53.3515
1993	39.0924
1994	23.91882
1995	17.22972
1996	13.60378
1997	9.3561
1998	3.37054
1999	13.23564
2000	8.81969
2001	13.15801
2002	19.88245
2003	20.98269
2004	30.02342
2005	36.52341
2006	48.55722
2007	62.77544
2008	57.72935
2009	54.75109
2010	42.82607
2011	32.60223
2012	30.19059
2013	31.94548
2014	33.13517
2015	32.09987
2016	37.20544