Year | Value | 2021 | 18.198589441131 | 2020 | 16.983262295899 | 2019 | 18.144377190387 | 2018 | 18.545967473162 | 2017 | 18.887486060685 | 2016 | 17.590229809729 | 2015 | 18.51578985531 | 2014 | 18.301936135827 | 2013 | 16.503270612339 | 2012 | 17.483233556746 | 2011 | 18.02201327978 | 2004 | 17.965075861919 | 2003 | 17.196137740543 | 2002 | 16.484242269375 | 1998 | 14.568944102607 | 1997 | 9.9048369571779 | 1996 | 8.861718691586 | 1995 | 13.600788301997 |
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