Year	% of expense
1990	13.194077942279382
1991	10.444122372397677
1992	12.265782823713527
1993	11.484753743351002
1994	11.281034065070521
1995	15.05348062423286
1996	14.374673267935666
1997	14.818698675985193
1998	15.521762761146757
1999	13.68933391045458
2000	13.85627966361509
2001	14.699472407715605
2002	15.480352726402389
2003	15.421972243935834
2004	15.61142789116099
2005	15.880246509211343
2006	16.224198053531637
2007	16.110720707766905
2008	16.07262106144963
2009	15.518744600306466
2010	14.35883323312106
2011	14.459121038235203
2012	15.214151246205112
2013	15.598979496310076
2014	15.83534477400394
2015	14.940267409195073
2016	15.81421263285024
2017	15.980212506416532
2018	15.985063195542299
2019	16.28260648346023
2020	15.070637141253297
2021	15.226760140297724
2022	15.079781017271147