Year	Percent
1970	11.93574
1971	8.24003
1972	4.40527
1973	15.82815
1974	4.01071
1975	9.58096
1976	12.85576
1977	10.94891
1978	7.39744
1979	5.89849
1980	6.4602
1981	6.50075
1982	6.7707
1983	6.21825
1984	6.45886
1985	6.89609
1986	6.83056
1987	7.78461
1988	8.17476
1989	7.35784
1990	5.49125
1991	5.23105
1992	2.07856
1993	3.97456
1994	6.31854
1995	9.02841
1996	5.72745
1997	9.48536
1998	8.74629
1999	8.86325
2000	3.95638
2001	10.40402
2002	6.84108
2003	8.27903
2004	4.52924
2005	8.78353
2006	13.82853
2007	17.02149
2008	18.59238
2009	19.8551
2010	16.47483
2011	13.4394
2012	57.87725
2013	4.31364
2014	8.06457
2015	7.69797
2016	2.86509
2017	8.37591