Year	% of expense
1972	35.714285714285715
1973	48
1974	40
1975	40.38461538461539
1976	40.27777777777778
1977	35.51401869158878
1978	31.446540880503143
1979	38.98809523809524
1980	37.06467661691542
1981	28.448275862068968
1982	26.266544956640804
1983	24.603989439718394
1984	25.833197854007476
1985	28.468253565446886
1986	28.652737833630482
1987	24.08374689826303
1988	24.958143260992976
1989	23.584440695315905
1990	23.448554564547987
1991	21.738154053447115
1992	21.398702235039654
1993	19.910461549394196
1994	19.520613039085244
1995	17.825842376018066
1996	18.63159981678095
1997	18.167848480921258
1998	17.971692060498874
1999	17.07966287564807
2000	12.247904002492449
2001	12.13764740158342
2002	12.343012386520336
2003	13.015759068497262
2004	12.291996382456889
2005	12.83672751909318
2006	13.02952590278618
2007	13.413928842502731
2008	12.839763577889784
2009	13.075143691573498
2010	13.441775469021369
2011	13.658694480956434
2012	13.657616873940764
2013	13.567400822886741
2014	14.360056789998902
2015	14.219823530825106
2016	14.182243375438947
2017	13.932386078138578
2018	14.16700207473668
2019	14.163923887718802
2020	13.075490864557274
2021	13.725274654158193
2022	13.286534185979896