Year	Percent
1980	-49.90105
1981	-49.22611
1982	-56.26106
1983	-53.18088
1984	-54.92734
1985	-56.54433
1986	-57.8328
1987	-47.63454
1988	-42.7863
1989	-42.9869
1990	-51.68765
1991	-47.82582
1992	-49.37387
1993	-33.78477
1994	-41.47084
1995	-43.24165
1996	-35.09165
1997	-31.09589
1998	-36.28911
1999	-39.01713
2000	-33.50617
2001	-32.5449
2002	-35.99979
2003	-36.03968
2004	-37.55882
2005	-28.78912
2006	-27.55229
2007	-30.18942
2008	-26.19245
2009	-25.88233
2010	-29.09771
2011	-28.81067
2012	-19.41353
2013	-14.3542
2014	-20.32416
2015	-14.2512
2016	-20.99861
2017	-24.81507