Year	Percent
1971	88.79649
1972	87.13011
1973	84.92204
1974	86.90808
1975	78.92638
1976	77.35913
1977	71.37241
1978	76.75545
1979	83.12119
1980	73.44852
1981	90.23642
1982	78.99704
1983	78.44166
1984	76.26992
1985	58.44519
1986	61.01412
1987	68.77114
1988	77.60135
1989	76.51376
1990	78.72302
1991	83.92305
1992	81.66694
1993	100.55854
1994	104.52595
1995	99.81298
1996	96.12532
1997	99.21381
1999	99.82805
2000	97.27323
2001	98.57838
2002	100.90276
2003	103.19252
2004	86.99913
2005	99.85102
2006	101.41141
2007	99.95973
2008	99.67638
2009	103.32212
2010	100.85892
2011	101.55157
2012	99.69033
2013	97.85683
2014	100.09721
2015	97.79705