Year	% of expense
1990	21.977698955495896
1991	32.880077967704096
1992	29.034632529431935
1993	22.329390287616917
1994	19.952526418673397
1995	14.311724542985097
1996	24.306171103707552
1997	16.008486858816322
1998	18.74584849245739
1999	17.392667306460172
2000	17.27014589010957
2001	18.85420705699884
2002	14.670988736161695
2003	11.786975102552733
2004	12.305999479957785
2005	12.377670572019298
2006	14.514670322618214
2007	12.554779878670175
2008	15.77014922878995
2009	12.66576029084892
2010	12.801765996600295
2011	16.871368862845724
2012	16.150237565246815
2013	15.495750620843781
2014	15.621555653475458
2015	15.511055680928692
2016	18.029339539730447
2017	16.589407275241054
2018	15.438447224037214
2019	16.33908803941458
2020	15.779006173834684
2021	15.901063342986504
2022	16.109141802774914