Year	Percent
1970	0.59736
1971	0.55148
1972	0.21285
1973	0.23113
1974	0.33056
1975	0.283
1976	0.16296
1977	0.33383
1978	0.45995
1979	0.45454
1980	0.47046
1981	0.72825
1982	0.93923
1983	1.59567
1984	1.52667
1985	2.9317
1986	1.92888
1987	0.87702
1988	0.51769
1989	1.45675
1990	1.24149
1991	1.10792
1992	1.47871
1993	1.71874
1994	1.77042
1995	1.0468
1996	3.20263
1997	5.21493
1998	2.87355
1999	1.74959
2000	2.43923
2001	2.58844
2002	2.17872
2003	1.81708
2004	2.66123
2005	6.98348
2006	4.15192
2007	4.28402
2008	4.32988
2009	3.43619
2010	2.2402
2011	4.36676
2012	4.06843
2013	4.26348
2014	4.27478
2015	4.02142
2016	4.94484
2017	4.53227