Year	Percent
1971	98.9877
1972	99.34137
1973	97.58239
1974	97.95021
1975	99.47064
1976	99.88381
1977	101.55362
1978	101.75913
1979	100.90919
1980	98.85792
1981	99.72508
1982	100.64791
1984	100.30718
1985	99.79716
1986	97.32209
1987	98.08267
1988	96.27088
1989	95.0076
1990	95.122
1991	99.90063
1992	101.1969
1993	99.98057
1998	97.69038
1999	97.63311
2000	97.92279
2001	101.54751
2002	102.71236
2003	103.50533
2004	102.60324
2005	100.05779
2006	97.57623
2007	97.81046
2008	99.15657
2009	101.25982
2010	99.35865
2011	97.66902
2012	99.7706
2013	101.05466
2014	98.26277
2015	97.96806
2016	100.85543