| Year | Value | | 2020 | 16.248996539409 | | 2019 | 13.9477004916 | | 2018 | 21.248477310555 | | 2017 | 16.312401742158 | | 2016 | 17.050477653774 | | 2015 | 16.244553679373 | | 2014 | 16.435863231529 | | 2013 | 45.822443769184 | | 2012 | 47.881904410439 | | 2011 | 45.199295126027 | | 2010 | 51.855190979277 | | 2009 | 38.74634139762 | | 2008 | 46.083420709409 | | 2007 | 57.263770513597 | | 2006 | 59.926282753084 | | 2005 | 61.754839536772 | | 2004 | 62.201613475597 | | 2003 | 53.848890470049 | | 2002 | 50.338573226385 | | 2001 | 49.240264193164 | | 1999 | 26.293719622606 | | 1998 | 26.066076968777 | | 1997 | 26.71706337045 | | 1996 | 28.806022626212 | | 1995 | 29.206891430269 | | 1994 | 32.112209075543 | | 1993 | 31.545670597731 | | 1992 | 24.942319368549 | | 1991 | 21.343607031062 | | 1990 | 17.9717999357 |
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