Year	Percent
1972	4.69896
1973	13.29974
1974	45.59879
1975	39.78658
1976	20.69857
1977	17.60009
1978	8.70127
1979	1.69167
1980	-1.67294
1981	-43.40667
1982	-39.592
1983	-32.59048
1984	-12.30298
1985	-16.47391
1986	-10.09
1987	-80.64833
1988	-63.43636
1989	-72.56115
1990	-97.63647
1991	-72.78148
1992	-102.33
1993	-82.69913
1994	-62.46587
1995	-83.98684
1996	-78.96
1997	-71.78286
1998	-63.18731
1999	-75.09533
2000	-81.37155
2001	-82.1123
2002	-90.59953
2003	-75.42301
2004	-78.82617
2005	-96.95572
2006	-79.77878
2007	-71.95089
2008	-73.308
2009	-71.71333
2010	-66.57904
2011	-70.44858
2012	-79.57294
2013	-80.23865
2014	-82.0409
2015	-93.62938
2016	-84.51289
2017	-85.48992