| Year | Value | | 2014 | -74.752393994171 | | 2013 | -88.424739689246 | | 2012 | -42.20311455639 | | 2011 | -43.844939361752 | | 2010 | -10.218029951342 | | 2009 | -4.6358859697482 | | 2008 | -3.2849150002043 | | 2007 | -7.631586106368 | | 2006 | -3.3105733359672 | | 2005 | -3.3039691452692 | | 2004 | 1.2284471434612 | | 2003 | 3.8006159012853 | | 2002 | 4.6895696455831 | | 2001 | 5.3516417969066 | | 2000 | 4.7053907471034 | | 1999 | 4.0458240227371 | | 1998 | 7.8063640170451 | | 1997 | 5.6202477341718 | | 1996 | 7.5403901250322 | | 1995 | 8.9138715246183 | | 1994 | 8.7056516381908 | | 1993 | 11.726408620179 | | 1992 | 11.757521736292 | | 1991 | 11.417097893039 | | 1990 | 12.96736142633 | | 1989 | 12.22663346549 | | 1988 | 11.926336010354 | | 1987 | 9.1189981490717 | | 1986 | 10.931830515437 | | 1985 | 11.637139755958 | | 1984 | 11.864184280442 | | 1983 | 12.021797567843 | | 1982 | 9.3161134768059 | | 1981 | 9.7911467627355 | | 1980 | 10.3870838424 | | 1979 | 10.484318137048 | | 1978 | 9.8229007643861 | | 1977 | 7.7095833926521 | | 1976 | 8.2256817300213 | | 1975 | 8.0854003673463 | | 1974 | 8.372084505606 | | 1973 | 7.476843262691 | | 1972 | 7.4769278083826 | | 1971 | 6.4106999289979 |
|