Year | Value | 2014 | 19.971622947488 | 2013 | 19.892436570194 | 2012 | 19.858930425188 | 2011 | 22.250411481983 | 2010 | 23.984708717373 | 2009 | 26.10268086688 | 2008 | 16.53000190114 | 2007 | 14.588534463601 | 2006 | 13.854305083457 | 2005 | 15.650689046719 | 2004 | 16.545446185197 | 2003 | 17.548542814474 | 2002 | 15.09808714363 | 2001 | 14.327314724893 | 2000 | 16.394707817557 | 1999 | 18.615077175749 | 1998 | 16.035639077587 | 1997 | 14.43505591232 | 1996 | 19.0074451578 | 1995 | 13.357905731886 | 1994 | 13.895711602496 | 1993 | 6.5297254081791 | 1992 | 11.071719815646 | 1991 | 13.898945148984 | 1990 | 16.545312054716 | 1989 | 15.718956701616 | 1988 | 15.869105567321 | 1987 | 16.635255266274 | 1986 | 16.174807742516 | 1985 | 11.450672707123 | 1984 | 12.760929296311 | 1983 | 12.279149001988 | 1982 | 16.494253295172 | 1981 | 14.758470558235 | 1980 | 15.449293612382 | 1979 | 17.214616623536 | 1978 | 14.728561762716 | 1977 | 14.580425548399 | 1976 | 12.216506897358 | 1975 | 14.11257905887 | 1974 | 12.650016957127 | 1973 | 13.89243237159 | 1972 | 15.78905759029 | 1971 | 15.492196110646 |
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