Year | Value | 2022 | 2.3800071549157 | 2021 | 2.406363381014 | 2020 | 2.4406088847732 | 2019 | 2.4482006983456 | 2018 | 2.4966449040885 | 2017 | 2.5273169197177 | 2016 | 2.5070340856256 | 2015 | 2.5411874624474 | 2014 | 2.6281238528085 | 2013 | 2.6974740433916 | 2012 | 2.7492888776324 | 2011 | 2.764062378553 | 2010 | 2.744378852237 | 2009 | 2.7273848429788 | 2008 | 2.7196868027914 | 2007 | 2.709626937306 | 2006 | 2.695925823028 | 2005 | 2.6936934175426 | 2004 | 2.6955034650786 | 2003 | 2.6927679061612 | 2002 | 2.6828899560603 | 2001 | 2.6512654944806 | 2000 | 2.6028687696143 | 1999 | 2.5426198869362 | 1998 | 2.5160338964463 | 1997 | 2.522964745178 | 1996 | 2.5268525941951 | 1995 | 2.557189798156 | 1994 | 2.5748294487359 | 1993 | 2.5557676243051 | 1992 | 2.5237279625411 | 1991 | 2.5622012363841 | 1990 | 2.6285989548554 | 1989 | 2.6136445676367 | 1988 | 2.5868440307457 | 1987 | 2.5771031927461 | 1986 | 2.6200700446938 | 1985 | 2.725926465438 | 1984 | 2.4719382256575 | 1983 | 2.505583858711 | 1982 | 2.9008718733798 | 1981 | 3.0029876235511 | 1980 | 3.0637124877311 | 1979 | 3.0378394955675 | 1978 | 3.0229245629864 | 1977 | 2.9432522580838 | 1976 | 2.8344902652352 | 1975 | 2.7312258729376 | 1974 | 2.5712605452729 | 1973 | 2.4311279722006 | 1972 | 2.3237341146533 | 1971 | 2.2568082219469 | 1970 | 2.1987856550446 | 1969 | 2.1393801069756 | 1968 | 2.0955410324412 | 1967 | 2.1069660359842 | 1966 | 2.1685631163424 | 1965 | 2.1653891801485 | 1964 | 2.1386308499224 | 1963 | 2.1147815356106 | 1962 | 2.0854566981797 | 1961 | 2.0426479987353 |
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