Year	% of expense
1990	21.387967209915097
1991	21.031125224741402
1992	17.47882187938289
1993	12.12558033184543
1994	10.071902705788121
1995	10.767433180246993
1996	10.841525729188016
1997	13.7573457897837
1998	11.79386521475499
1999	12.599473782880487
2000	12.852839931153184
2001	12.184484957174382
2002	9.175670060253479
2003	8.015455326500815
2004	6.195581946281881
2005	6.508894336539066
2006	7.606861561869025
2007	7.80664623169367
2008	7.711305696732186
2009	7.7059100911663
2010	7.863190378224402
2011	7.1025780952853435
2012	8.989422394917815
2013	11.473749805265617
2014	12.876670421203398
2015	12.987934705464868
2016	11.403760291647892
2017	11.338171800916482
2018	12.40458486697463
2019	13.423441889627066
2020	14.227191065237044
2022	14.318669635513832