Year	% of expense
1990	43.54886439298661
1991	44.83659255290651
1992	35.76346201131055
2014	22.15955387191525
2015	23.110621308692846
2016	21.59770577380312
2017	20.58964112980225
2018	19.961133347793435
2019	17.183634743117445
2020	16.392007671384064