Year | Value | 2022 | 14 | 2021 | 16.4 | 2020 | 19.3 | 2019 | 13.7 | 2018 | 12.2 | 2017 | 12.1 | 2016 | 12.9 | 2015 | 13 | 2014 | 14.3 | 2013 | 15.3 | 2012 | 16.8 | 2011 | 17.9 | 2010 | 20 | 2009 | 22.2 | 2008 | 24.1 | 2005 | 25.6 | 2004 | 28.8 | 2003 | 29.3 | 2002 | 30.9 | 2001 | 39.5 | 2000 | 33.2 | 1999 | 38.2 | 1996 | 34.2 | 1992 | 23.9 | 1991 | 27.3 | 1989 | 29.5 | 1988 | 29.5 | 1980 | 37.1 |
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