Year	% of expense
1990	55.61611277301971
1991	53.71271659880693
1992	59.185812510481306
1993	60.60358890701468
1994	47.49743269187838
1995	40.40212916372104
1998	38.42276904832494
1999	37.091547394004856
2012	35.96444097924468
2013	36.6651630831259
2014	36.85782298203852
2015	38.500887799103744
2016	39.511867818502054
2017	43.86386295658479
2018	39.93786359310085
2019	35.380666707593946
2020	37.1678236743041
2021	34.66851907050393