Year | Value | 2014 | 8.9393550917868 | 2013 | 19.02767036666 | 2012 | 25.628977005279 | 2011 | 30.542882846675 | 2010 | 31.432955121632 | 2009 | 22.413709678837 | 2008 | 36.560204032731 | 2007 | 37.136542783734 | 2006 | 40.704298093978 | 2005 | 40.639351133984 | 2004 | 35.660956333143 | 2003 | 29.754937636518 | 2002 | 30.321640732638 | 2001 | 29.082179140907 | 2000 | 34.466997872125 | 1999 | 28.706233465218 | 1998 | 25.948948599669 | 1997 | 31.962557049343 | 1996 | 31.697231799705 | 1995 | 23.510138561319 | 1994 | 21.850464751592 | 1993 | 17.691155612165 | 1992 | 20.20386706985 | 1991 | 24.466708060466 | 1990 | 29.550646752025 | 1989 | 22.276413274707 | 1988 | 20.391442407559 | 1987 | 23.981542773696 | 1986 | 19.642746654892 | 1985 | 26.185660400094 | 1984 | 27.243107529979 | 1983 | 4.1523002354626 | 1982 | 12.111732150459 | 1981 | 19.972265855095 | 1980 | 24.249275179877 | 1979 | 23.687884199733 | 1978 | 19.670531172365 | 1977 | 25.069811054166 | 1976 | 27.223842373283 | 1975 | 30.987061592914 | 1974 | 39.20166794376 | 1973 | 25.956206571744 | 1972 | 23.114695457058 | 1971 | 23.566790920705 | 1970 | 24.403652090341 |
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