| Year | Value | | 2020 | 141.08598029415 | | 2019 | 130.30113982909 | | 2018 | 127.65264817398 | | 2017 | 123.09455717779 | | 2016 | 119.67566778006 | | 2015 | 120.90342014867 | | 2014 | 116.20642154095 | | 2013 | 114.6180056233 | | 2012 | 109.85161176587 | | 2011 | 102.55926772231 | | 2010 | 100 | | 2009 | 102.46388631623 | | 2008 | 77.768829432973 | | 2007 | 56.780174991959 | | 2006 | 53.911746462573 | | 2005 | 54.102981837132 | | 2004 | 53.616578819232 | | 2003 | 51.62523654937 | | 2002 | 49.974792121113 | | 2001 | 49.887489015336 | | 2000 | 47.077160467472 | | 1999 | 44.300090245618 | | 1998 | 41.656053327805 | | 1997 | 40.608416058483 | | 1996 | 40.358978613407 | | 1995 | 40.807966014545 | | 1994 | 40.907740992575 | | 1993 | 40.209316146361 | | 1992 | 39.660553767192 | | 1991 | 38.413366541809 | | 1990 | 37.665054206579 | | 1989 | 36.255132391359 | | 1988 | 35.691163665271 | | 1987 | 35.046627978314 | | 1986 | 34.160391408747 | | 1985 | 34.079824447877 | | 1984 | 33.797840084834 | | 1983 | 32.468485230484 | | 1982 | 30.615445130481 | | 1981 | 30.897429493525 | | 1980 | 27.942056721712 | | 1979 | 24.603044562078 | | 1978 | 21.873228616371 | | 1977 | 19.567536616908 | | 1976 | 17.021292749726 | | 1975 | 14.818038130851 | | 1974 | 12.492932068573 | | 1973 | 10.040558943047 | | 1972 | 8.4916917058449 | | 1971 | 7.021350954444 | | 1970 | 6.1268710989519 |
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