Year	% of expense
1990	24.15853658536585
1991	25.185732463161354
1992	24.451865280030532
1993	23.92211180724444
1994	23.872560017949294
1995	22.1632320098426
1997	21.10441411097323
1998	19.60346468908294
1999	18.94430124397624
2002	15.035846822207372
2003	15.007335612633154
2004	14.036983884622984
2005	11.223259444065743
2006	12.126191257104754
2007	11.574813462836087
2008	9.462810032459121
2009	8.938431351164187
2010	8.266788535264801
2011	7.565493373015792
2012	7.958274899181536
2013	9.000628776861012
2014	9.736587466247924
2015	10.976314129791232
2016	10.877238423752878
2017	10.39211494762048
2018	9.985820715839722
2019	10.164540087668037
2020	9.178981460306295
2021	8.287409685446024
2022	7.619972328377171