Year	% of expense
1997	50.145539638148506
1998	48.63186813186813
1999	45.69898065321406
2011	30.87436934237023
2012	29.1553330464777
2013	29.230393725965477
2014	29.39173075715359
2015	36.78362627705081
2016	39.3190344799477
2017	36.60080382546207
2018	36.64475930562385
2019	40.09362538002592
2020	37.44049835414751
2021	30.568446032710355
2022	33.64691928897216