| Year | Value | | 2022 | 1.6643784219331 | | 2021 | 1.3537028196967 | | 2020 | 1.7336075217249 | | 2019 | 1.9173360065035 | | 2018 | 1.7938088169829 | | 2017 | 1.809842924354 | | 2016 | 1.5996462431592 | | 2014 | 1.3385981974008 | | 2013 | 1.0452311825973 | | 2012 | 1.6239843687231 | | 2011 | 0.97604197877407 | | 2010 | 0.87650323651909 | | 2009 | 0.73526236138912 | | 2008 | 0.73944643123804 | | 2005 | 0.71521176883033 | | 2004 | 1.0911872973943 | | 2003 | 0.93176362655435 | | 2002 | 0.96334795526051 | | 2001 | 1.3201597828555 | | 2000 | 1.164610816384 | | 1999 | 1.1669080959279 | | 1998 | 1.0612244897959 | | 1997 | 0.932594644506 | | 1996 | 0.86140147115757 | | 1995 | 0.97097625329815 | | 1994 | 1.2323719984754 | | 1987 | 0.6352103960396 | | 1986 | 0.76950354609929 | | 1985 | 0.74383561643836 | | 1984 | 0.72775689223058 | | 1983 | 0.68519866103915 | | 1982 | 0.63348416289593 | | 1981 | 0.63175394846218 | | 1980 | 0.67139127191347 | | 1979 | 0.83912454873646 | | 1978 | 0.92817371937639 | | 1977 | 0.93663434903047 | | 1976 | 0.82177385456074 | | 1975 | 0.87084257206208 |
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