Year | Value | 2014 | 16.841702642625 | 2013 | 14.978323771416 | 2012 | 17.791586648974 | 2011 | 16.935741261027 | 2010 | 14.528703579379 | 2009 | 12.358457600592 | 2008 | 12.821796582201 | 2007 | 13.634140163356 | 2006 | 13.724553401098 | 2005 | 15.047354197694 | 2004 | 16.028714335142 | 2003 | 18.470235220475 | 2002 | 18.05880742125 | 2001 | 18.820144540341 | 2000 | 17.007418104415 | 1999 | 18.185585538624 | 1998 | 21.336205052952 | 1997 | 21.594699019784 | 1996 | 18.954217227537 | 1995 | 19.655404422073 | 1994 | 14.777146674936 | 1993 | 14.554455183732 | 1992 | 14.240146640889 | 1991 | 13.605812503838 | 1990 | 15.529171645936 | 1989 | 15.462557680045 | 1988 | 14.760753176508 | 1987 | 16.280361498311 | 1986 | 15.983675141166 | 1985 | 15.40536564277 | 1984 | 15.264645321667 | 1983 | 16.11291431159 | 1982 | 19.064391532668 | 1981 | 19.778924697173 | 1980 | 19.724503952515 | 1979 | 18.696706633927 | 1978 | 18.498557922595 | 1977 | 17.773042220817 | 1976 | 19.170958531854 | 1975 | 18.909957911671 | 1974 | 16.55461823728 | 1973 | 15.904799412682 | 1972 | 14.267648022885 | 1971 | 14.729219883402 |
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