Year % 2001 16.35972075511784 2002 14.958176027991213 2003 15.187909424971714 2004 18.574989317214385 2005 18.66268744163905 2006 18.0391506361984 2007 18.45203923489887 2008 17.192778101339545 2009 21.04561979143744 2010 20.391554863157545 2011 20.326994927242367 2012 19.357321754918875 2013 20.596504438583043 2014 20.21252105768907 2015 20.86006780288683 2016 21.018429557699744 2017 20.857446590732327 2018 19.564268478809467 2019 20.192352948837737 2020 21.651190295474255 2021 22.662854473801485 2022 22.17280478489822 2023 20.738920186816785