Year	% of expense
1990	18.188584042888678
1991	18.80553333052596
1992	18.530721107646446
1993	16.828081861606556
1994	18.042478806784672
1995	23.392885995891326
1996	21.720728281096072
1997	19.264109729219143
1998	19.807458826609135
1999	16.912961589923214
2000	21.521268426987277
2001	19.60053588105589
2002	13.830092559374327
2003	12.560757980932577
2004	13.47301379100121
2005	11.356722242072985
2006	12.550043123978218
2007	10.938251401919965
2008	14.308962662163328
2009	10.706719255260257
2010	8.117761582393504
2011	9.728537030531015
2012	10.341961108568222
2013	8.486158001350438
2014	10.627737509346147
2015	10.666626637045127
2016	8.460953530041792
2017	7.619900299715275
2018	7.669124035233564
2019	8.202060165427062
2020	6.039426759141834
2021	5.537312226518535
2022	4.786243120137837