Year	% of expense
1973	6.539139374357444
1974	7.608475116663262
1975	9.115345429320845
1976	11.153469315044115
1977	11.869302020275667
1978	10.011146795572175
1979	9.784292082723686
1980	10.627339042182047
1986	16.6283044822467
1987	14.816203515903048
1988	17.681914856879384
1989	18.923904633022172
1990	21.006932813957793
1991	21.188727558200092
1992	22.370338071415897
1993	22.99777451290346
1994	22.327187495004157
1995	22.627117932175768
1996	22.710446942692624
1997	19.847825689768225
1998	18.733287167740905
1999	15.340682693584807
2000	15.18932075479397
2001	14.77320208072189
2002	13.452175234578604
2003	12.19663576024725
2004	11.467652429835292
2005	11.131484870772967
2006	10.691342026403175
2007	11.396271471258993
2008	11.381382645940613
2009	9.519935375085137
2010	9.602442310149002
2011	10.59621059215651
2012	11.383183401065171
2013	10.658860845684197
2014	10.148349319918962
2015	9.196962415220609
2016	8.841237394385391
2017	8.577437021986443
2018	8.420285855310295
2019	7.821823231691666
2020	6.717676850051728
2021	6.914646712382433
2022	8.503817871248804