Year	Percent
1970	0.10518
1971	0.05377
1972	0.06274
1973	0.0663
1974	0.08762
1975	0.14847
1976	0.16302
1977	0.08743
1978	0.06353
1979	0.06206
1980	0.13388
1981	0.13408
1982	0.26148
1983	0.14263
1984	0.14472
1985	0.13877
1986	0.15065
1987	0.23447
1988	0.32913
1989	0.35621
1990	0.65824
1991	0.77173
1992	0.34831
1993	0.82396
1994	0.68178
1995	0.80169
1996	1.12963
1997	2.51464
1998	3.53357
1999	7.12711
2000	9.92142
2001	5.37021
2002	4.69076
2003	3.73745
2004	5.80319
2005	3.80746
2006	8.32711
2007	9.91331
2008	4.62784
2009	1.06038
2010	2.64241
2011	3.02318
2012	-0.18842
2013	2.02287
2014	3.06312
2015	5.44227
2016	4.07938
2017	2.03673