Year	Percent
1974	12.37181
1975	18.66323
1976	23.23735
1977	41.5928
1978	47.90925
1979	45.15197
1980	43.77037
1981	39.86298
1982	37.44228
1983	39.49763
1984	33.04471
1985	40.30307
1986	40.95589
1987	41.20089
1988	41.9193
1989	37.56781
1990	33.79741
1991	36.07768
1992	35.8973
1993	31.39789
1994	34.10175
1995	30.07934
1996	23.35216
1997	22.29719
1998	26.40366
1999	38.90129
2000	38.89955
2001	42.3718
2002	48.53415
2003	38.67439
2004	34.36809
2005	37.39997
2006	32.87014
2007	32.32677
2008	30.12941
2009	41.5293
2010	36.51036
2011	30.83678
2012	26.93756
2013	29.65213
2014	25.71087
2015	10.75778
2016	39.32127