Year % 1997 16.001174398120973 1998 16.340129288911 1999 17.289859407717618 2000 18.04857173424628 2001 17.72833485725896 2002 19.24101908112141 2003 19.506881869492027 2004 20.088656054805554 2005 20.698845128812554 2006 21.09983246279689 2007 22.237555446032538 2008 22.38864800946 2009 23.087525844245352 2010 23.16701112095266 2011 23.963768829378754 2012 25.027074923697942 2013 26.165650206570923 2014 26.790902715158797 2015 27.843294023585855 2016 27.96559311862373 2017 28.871681415929203 2018 29.87486451867179 2019 30.80181245074862 2020 31.499013806706113 2021 32.42340926944226 2022 32.52212389380531 2023 32.828637320766056