Year | Value | 2020 | 14.040255792012 | 2019 | 17.594660553746 | 2018 | 17.837270495773 | 2017 | 17.129171979892 | 2016 | 16.800185344777 | 2015 | 16.906708763825 | 2014 | 18.337570094704 | 2013 | 18.229817831836 | 2012 | 17.381915904039 | 2011 | 16.442348160511 | 2010 | 16.194535048311 | 2009 | 16.496198049228 | 1999 | 17.12485184864 | 1998 | 17.735521870422 | 1997 | 18.091501613618 | 1996 | 18.571917808219 | 1995 | 17.901477480056 | 1990 | 20.185138347918 |
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