Year	Percent
1977	-32.47945
1978	-18.22488
1979	-33.28294
1980	-36.63656
1981	-22.78386
1982	-22.39298
1983	-18.70099
1984	-10.61258
1985	-4.43503
1986	-5.89704
1987	-12.93486
1988	-5.86941
1989	-21.7588
1990	-9.19434
1991	-16.2883
1992	-8.53458
1993	-15.17274
1994	-19.97482
1995	-12.08828
1996	-11.17738
1997	-23.1773
1998	-24.5169
1999	-16.06913
2000	-5.31344
2001	-7.79358
2002	-7.90374
2003	-14.22633
2004	-16.79727
2005	-16.45982
2006	-18.63697
2007	-29.13252
2008	-31.72846
2009	-29.00125
2010	-30.23839
2011	-28.66681
2012	-30.41069
2013	-32.78601
2014	-31.16098
2015	-17.4743
2016	-16.64248
2017	-14.54034