| Year | Value | | 2022 | 7.8326912423332 | | 2021 | 1.2656571906904 | | 2020 | 0.012438329957531 | | 2019 | 0.33817841004603 | | 2018 | 0.99371568346833 | | 2017 | 1.3686141164347 | | 2016 | 0.60739707464172 | | 2015 | 0.48793862390472 | | 2014 | 0.27815336746743 | | 2013 | 0.27441666666666 | | 2012 | 2.7733385405159 | | 2011 | 3.6530110043072 | | 2010 | 1.4025728989537 | | 2009 | 0.83553002150416 | | 2008 | 2.5885065765796 | | 2007 | 2.4539652813874 | | 2006 | 3.1076654587105 | | 2005 | 2.2771639488783 | | 2004 | 2.365362040973 | | 2003 | 3.2189909068289 | | 2002 | 3.6003465829091 | | 2001 | 4.3699033055179 | | 2000 | 2.8530303928716 | | 1999 | 2.3400949031217 | | 1998 | 2.5727522590913 | | 1997 | 2.3368629831412 | | 1996 | 3.0689773250979 | | 1995 | 4.2228161409949 | | 1994 | 5.4204401924163 | | 1993 | 6.7837799466541 | | 1992 | 9.5592603317751 | | 1991 | 11.849484177368 | | 1990 | 13.630570569307 | | 1989 | 12.686303645615 | | 1988 | 10.101632115227 | | 1987 | 9.6348318624575 | | 1986 | 12.331333489722 | | 1985 | 19.46141000787 | | 1984 | 28.38463888971 | | 1983 | 24.002762380292 | | 1982 | 21.679283727709 | | 1981 | 19.040410746691 | | 1980 | 15.867480383609 | | 1979 | 21.899224806201 | | 1978 | 21.038772359938 | | 1977 | 31.016749098881 | | 1976 | 21.141904803196 | | 1975 | 15.271685751848 | | 1974 | 25.082777858953 | | 1973 | 12.974608523933 | | 1972 | 10.663355975948 | | 1971 | 11.946898365406 | | 1970 | 6.3801444900167 | | 1969 | 8.7827710555412 | | 1968 | 6.0813617114862 | | 1967 | 5.5264760075309 | | 1966 | 5.0392672185818 | | 1965 | 3.4249277774557 | | 1964 | 3.4448984822277 | | 1963 | 2.0215827275979 | | 1962 | 2.6620641793476 | | 1961 | 1.5489969698987 | | 1960 | 3.046592778327 |
|