Year	% of expense
1990	13.260664672376347
1991	18.58725499479216
1992	16.642210296830452
1993	13.21590758784886
1994	12.934768049292316
1995	14.11818522060964
1998	14.40853839312185
1999	16.945719686740482
2012	24.536989476747646
2013	28.208944280164022
2014	20.082233282839212
2015	18.212564471125393
2016	15.059129413738154
2017	9.312970180367987
2018	18.82212999522062
2019	24.893517807840833
2020	21.71989961131183
2021	23.485203398389658