Year % 1998 17.596707818930064 1999 18.59778597785981 2000 17.322834645669296 2001 17.61500240423145 2002 18.213660245183892 2003 16.85944619698565 2004 17.190872648782015 2005 17.294730392156858 2006 17.657483486386333 2007 18.03278688524589 2008 18.296284781594892 2009 18.552875695732833 2010 17.938538450227902 2011 17.92684689894461 2012 18.236732345750024 2013 19.316877152698066 2014 19.063245823389035 2015 19.762665449566427 2016 19.868637110016444 2017 20.128033348220914 2018 20.626015059796256 2019 20.85637317453565 2020 21.543129605548323 2021 21.573352232459246 2022 22.049969897652012 2023 22.799639531390824