Year	% of expense
1990	16.727451542843095
1991	15.322412650317204
1992	13.346889149756832
1993	10.995987831224372
1994	13.412510604098763
1995	17.37846716846176
1998	21.19774681292618
1999	22.846340804752906
2012	29.28184238433134
2013	31.425499291830718
2014	33.22224626704177
2015	33.360108226938365
2016	32.42472532080852
2017	32.828786368168224
2018	34.22655649478531
2019	31.232266546529907
2020	33.52979868079969
2021	33.62178882435661