Year	% of expense
1972	15.789473684210526
1973	13.88888888888889
1974	14.285714285714285
1975	13.043478260869565
1976	12.777777777777777
1977	9.583333333333334
1978	10.472972972972974
1979	10.14851485148515
1980	9.551656920077972
1981	11.931119311193111
1982	5.468066491688539
1983	5.980739989863153
1984	6.725602357427631
1985	6.390831390831391
1986	6.175308521535535
1987	4.957354158419404
1988	6.769327850832553
1989	7.735655737704918
1990	7.512186489486639
1991	10.434942924303646
1992	10.392792696812512
1993	10.43269599259482
1994	10.639501689667055
1995	8.795023657960005
1996	9.181140079249813
1997	9.109987007863445
1998	7.572427460782816
1999	7.275905518693053
2000	7.868981093662189
2009	7.288519087935049
2010	6.992737779779272
2011	6.923590192540003
2012	7.049697776348994
2013	6.935858755438725
2014	7.037944031202245
2015	7.5918813094409305
2016	7.220112320683681
2017	6.866764620984908
2018	7.114517133739384
2019	6.021278219550582
2020	5.5983882118992545
2021	6.84101577427168
2022	6.58490510807125