Year	Percent
1980	-16.49744
1981	-15.80479
1982	-17.90075
1983	-16.64639
1984	-14.21428
1985	-8.60653
1986	-9.50169
1987	-24.74387
1988	-29.22665
1989	-30.42545
1990	-27.89408
1991	-34.98043
1992	-43.57974
1993	-40.84498
1994	-39.75927
1995	-43.70547
1996	-27.36982
1997	-22.07032
1998	-19.26979
1999	-29.3546
2000	-26.73277
2001	-13.18348
2002	-31.59531
2003	-25.38106
2004	-19.35524
2005	-15.98683
2006	-10.76802
2007	-9.07491
2008	-9.83629
2009	-11.30772
2010	-14.71111
2011	-21.48108
2012	-46.07753
2013	-53.63732
2014	-51.40402
2015	-39.77358
2016	-37.46149
2017	-32.37383