Year	Percent
1970	14.38305
1971	14.64135
1972	12.84333
1973	13.92624
1974	16.48012
1975	16.16261
1976	18.57339
1977	27.71262
1978	35.58215
1979	35.6697
1980	43.28815
1981	54.46632
1982	62.11957
1983	77.59892
1984	85.19669
1985	90.27415
1986	80.27068
1987	83.35896
1988	81.66808
1989	69.63164
1990	67.94273
1991	66.19458
1992	62.7401
1993	70.03714
1994	99.00176
1995	82.89708
1996	75.82931
1997	82.72202
1998	82.35653
1999	79.20428
2000	79.61354
2001	77.10699
2002	78.72001
2003	65.01078
2004	49.61822
2005	45.1588
2006	20.88902
2007	23.11062
2008	21.30678
2009	29.44019
2010	30.57371
2011	30.70653
2012	35.29042
2013	36.06788
2014	37.63726
2015	44.51807
2016	46.55899