Year	Percent
1977	53.59611
1978	50.35057
1979	34.21595
1980	44.81984
1981	59.40301
1982	48.96663
1983	34.39323
1984	30.1618
1985	28.05793
1986	21.48555
1987	13.67415
1988	9.67531
1989	8.95318
1990	11.05448
1991	27.07936
1992	21.65742
1993	62.60642
1994	19.84307
1995	18.16059
1996	38.09838
1997	39.27161
1998	27.29336
1999	31.52879
2000	28.90806
2001	24.9965
2002	37.16284
2003	23.74599
2004	18.72262
2005	30.36511
2006	13.14827
2007	27.86745
2008	14.56012
2009	13.42565
2010	16.71847
2011	7.87068
2012	11.17305
2013	13.6667
2014	10.75617
2015	11.18813
2016	15.10214