Year | Value | 2022 | 15.445073419241 | 2021 | 14.748760734756 | 2020 | 9.9419451985365 | 2019 | 10.353979292588 | 2018 | 12.20801705954 | 2017 | 11.377150797206 | 2016 | 8.2120499519724 | 2015 | 13.476640400465 | 2014 | 9.8196888036539 | 2012 | 12.03099702518 | 2011 | 10.800973117625 | 2010 | 13.843109431397 | 2009 | 13.873346406475 | 2008 | 11.807050582968 | 2007 | 12.792614493729 | 2006 | 10.458374884281 | 2005 | 8.5596286343695 | 2004 | 6.8405101044108 | 2003 | 4.4252977719676 | 1995 | 9.6375203567509 | 1994 | 13.809344670911 | 1993 | 12.352032938891 | 1992 | 10.658649010023 | 1991 | 9.4898991079395 | 1990 | 10.206890663434 | 1989 | 13.130236007399 | 1988 | 11.649347352349 | 1987 | 11.421065096913 | 1986 | 10.025584205364 | 1985 | 15.293140844665 | 1984 | 15.02726927883 | 1983 | 9.0623544260711 | 1982 | 9.4321332619431 | 1981 | 12.450543730727 | 1980 | 5.6127535283349 |
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