Year	Percent
1967	11.34021
1968	55.40025
1969	62.7
1970	54.02622
1971	33.65308
1972	15.625
1973	12.63282
1974	25.9631
1975	16.85994
1976	16.36321
1977	14.25856
1978	9.59325
1979	20.34897
1980	25.00362
1981	26.59833
1982	15.39434
1983	15.58451
1984	12.70144
1985	12.64505
1986	-1.67995
1987	19.81088
1988	8.6525
1990	19.63097
1991	8.32416
1992	9.16895
1993	4.99625
1994	8.21372
1995	8.47921
1996	14.04423
1997	11.44593
1998	-7.75505
1999	11.12481
2000	27.78444
2001	22.3684
2002	21.18814
2003	16.9628
2004	12.5084
2005	27.21948
2006	24.50819
2007	16.49384
2008	21.29976
2009	15.99007
2010	24.44208
2011	29.70963
2012	30.64673
2013	26.41506
2014	27.90146
2015	8.71631
2016	5.62933