Year	Percent
1970	100.75111
1971	109.35076
1972	105.2785
1973	103.76801
1974	95.19243
1975	88.2631
1976	92.14663
1977	91.15264
1978	88.23691
1979	91.90804
1980	90.62351
1981	83.23266
1982	82.79908
1983	74.23176
1984	84.64596
1985	74.07412
1986	58.34133
1987	57.76262
1988	57.58351
1989	61.83808
1990	75.87862
1991	71.62037
1992	76.58752
1993	71.76599
1994	69.70011
1995	86.61927
1996	80.74539
1997	78.70557
1998	82.28759
1999	78.38212
2000	83.59286
2001	83.41096
2002	77.61956
2003	77.67307
2004	77.79826
2005	80.446
2006	82.93252
2007	82.10633
2008	82.5949
2009	74.57088
2010	78.48666
2011	86.0293
2012	89.47085
2013	82.47117
2014	78.57426
2015	67.16477
2016	58.58325
2017	57.82729