Year	% of expense
1998	13.557546840451531
1999	12.710563485363524
2000	13.85627966361509
2001	14.885145482388973
2003	16.60190286772896
2004	15.709536919744115
2005	17.49326006529764
2006	17.800838530538613
2007	17.63079243227405
2008	18.152973739283063
2009	17.46883176850854
2010	17.331253761797967
2011	16.765188018478963
2012	16.46144556999662
2013	15.722324948073457
2014	15.319740447592268
2015	14.445376568822507
2016	14.799684091967427
2017	15.14433059485124
2018	16.050941137082127
2019	15.811081584577597
2020	15.64561088154661
2021	15.817702172684902
2022	17.858340417184124