Year	Percent
1970	2.4326
1971	2.35608
1972	2.26044
1973	2.24455
1974	6.01111
1975	3.76921
1976	3.45027
1977	3.08907
1978	3.05648
1979	2.70329
1980	3.81372
1981	5.05783
1982	5.21256
1983	4.15374
1984	2.34942
1985	2.22663
1986	1.76269
1987	1.31342
1988	2.03964
1989	4.29326
1990	5.29812
1991	8.13639
1992	8.76053
1993	7.4829
1994	5.82964
1995	4.71027
1996	5.03536
1997	5.13624
1998	2.99774
1999	4.92143
2000	4.03843
2001	0.59703
2002	3.16613
2003	2.92094
2004	3.50787
2005	2.73439
2006	4.7272
2007	4.68689
2008	3.28079
2009	0.05669
2010	4.26859
2011	5.07443
2012	2.82906
2013	3.4943
2014	3.14127
2015	3.32525
2016	4.54248
2017	3.02438