Year	Percent
1970	17.1431
1971	20.66013
1972	15.44359
1973	21.72068
1974	29.46573
1975	9.75518
1976	21.45718
1977	15.36479
1978	25.02921
1979	31.28985
1980	31.92503
1981	-30.67358
1982	-40.08667
1983	-8.31075
1984	-4.00044
1985	-4.67166
1986	-9.93584
1987	-2.90511
1988	-3.12471
1989	-0.90504
1990	0.27035
1991	-1.21032
1992	-0.75633
1993	-0.3936
1994	-0.02845
1995	-0.01025
1996	-0.00856
1997	21.50585
1998	23.55482
1999	16.95517
2000	26.07095
2001	3.76653
2002	21.37806
2003	0.55091
2004	-7.69216
2005	-7.0468
2006	12.41337
2007	17.70683
2008	19.60107
2009	0.11284
2010	5.33618
2011	16.66372
2012	15.34848
2013	3.66506
2014	4.38955
2015	-6.00515
2016	-8.37767
2017	1.31332