Year	% of expense
1972	24.84557309540151
1973	24.181504882251577
1974	24.379432624113477
1975	23.524150268336314
1976	23.076923076923077
1977	23.173193379087607
1978	23.395784543325526
1979	23.340177960301165
1980	24.768330352788166
1981	25.03427116652523
1982	26.24941857460334
1983	24.268495428096426
1984	27.123432809464948
1985	24.812422144326312
1988	26.31197615636681
1989	27.397859784849082
1990	28.462624775193422
1991	30.39433684594975
1992	45.26399439455177
1993	43.011688191289835
1994	30.270097377212313
1995	15.607348978009671
1996	16.425785730672175
1997	16.810327026143483
1998	16.737896821650775
1999	16.187459628477395
2000	15.557614201757344
2001	15.674847166188052
2002	15.019831540528966
2003	14.604115945986065
2004	14.231179250077414
2005	14.306916377492005
2006	13.806352603536832
2007	13.772775028226247
2008	13.375816818500747
2009	13.261669724898056
2010	14.1913814246356
2011	13.378926585358144
2012	14.198515371973771
2013	14.184324817617524
2014	14.063675835618819
2015	14.083379039941308
2016	14.918581878145098
2017	14.671753062395098
2018	14.331235960646445
2019	14.183677921195038
2020	13.219562248085595
2021	13.688233685979467
2022	13.490825180504249