Year	% of expense
1972	3.480278422273782
1973	3.6297640653357535
1974	3.776683087027915
1975	3.598691384950927
1976	3.537532355478861
1977	3.032104637336504
1978	2.8346456692913384
1979	2.864833685829648
1980	2.93470286133529
1981	6.221327967806841
1983	7.7867445054945055
1984	9.718225885890556
1985	10.150926683019897
1986	15.52971169132496
1987	17.720639332870046
1988	18.051543684585663
1989	18.13818450825784
1990	20.768914740415596
1991	15.345529377691486
1992	13.09127926705124
1993	15.185955185955185
1994	20.913824150544933
1995	12.988078032239049
1996	13.335248026749774
1997	28.668696685436103
1998	39.29344257675051
2008	14.827397801015819
2009	12.553426631167468
2010	10.389383613405814
2011	9.478700177562027
2012	9.115463121221474
2013	7.557034545880817
2014	7.417549756832541
2015	6.6216098716900635
2016	6.201228638822117
2017	6.425555789044342
2018	8.29387411370037
2019	6.870877764052982
2020	9.011221452908485
2021	10.234370275953317
2022	15.858861139408212