Year % 1997 17.014880505035325 1998 17.05997294453631 1999 17.994739285161685 2000 19.57392279352875 2001 19.550492610837434 2002 20.283092238295215 2003 21.37759851070431 2004 22.07242514500705 2005 22.17839805825243 2006 22.884819131224457 2007 23.87653200181572 2008 24.15356711003628 2009 24.46792452830188 2010 24.377358490566035 2011 25.113327289211234 2012 26.037623171095838 2013 27.681764004767572 2014 28.240527688295742 2015 28.266543835406118 2016 28.28593389700231 2017 29.789522200030728 2018 30.51628764597418 2019 31.817483484406207 2020 32.406696360006144 2021 32.72143184947223 2022 32.579113924050645 2023 32.95364657490902