Year % of expense 1995 22.41092241092241 1996 21.720055827684806 1997 21.69045921548311 1998 22.932791101157886 1999 21.06676960335884 2000 22.406127596126964 2001 23.22200830861138 2002 25.263364000402188 2003 24.270154875743934 2004 23.8342418506436 2005 26.3096649287086 2006 24.163141806704562 2007 24.714074686728537 2008 23.400048736734416 2009 24.604579475221716 2010 22.509722306892485 2011 23.289497532975474 2012 23.665434334851675 2013 21.50495971199323 2014 22.026930822399333 2015 22.980096981646167 2016 21.952284778974942 2017 21.8211314503369 2018 23.215951888593455 2019 23.97524022224864 2020 22.758807414596355 2021 19.55904982429179 2022 21.701093541526202