Year % 2001 16.4078012980366 2002 14.924940080107003 2003 15.174277202772224 2004 17.468935469364066 2005 18.002896725357935 2006 16.838079724285667 2007 17.619667780241144 2008 15.971570204728428 2009 20.052060966265802 2010 20.12041804441661 2011 19.714822184479345 2012 18.897836589566438 2013 19.720240578639533 2014 19.39649838988274 2015 20.762102311467064 2016 20.905932630917167 2017 20.634741732254035 2018 19.432227553758015 2019 19.7805652631531 2020 21.563385523701655 2021 22.226700342439162 2022 21.389311852347554 2023 20.778729409550017