Year	% of expense
1972	3.7099179716629385
1973	3.8461538461538463
1974	3.8119440914866582
1975	4.431279620853081
1976	3.9818742768993443
1977	4.309453764808778
1978	4.599840467960649
1979	4.969505308335216
1980	7.167909894778441
1981	9.931034482758621
1982	10.397209406998988
1983	15.391984671882483
1984	17.7414142601134
1985	19.743852190116264
1986	16.624175164967006
1987	15.385913727003112
1988	12.194620758938763
1989	11.13600670086902
1990	11.685286078550071
1991	10.047082839457396
1992	9.131697820499172
1993	9.972847221274678
1994	12.779906113419306
1995	10.687728908407081
1996	11.700535195369879
1997	12.13432325900392
1998	10.599628400697584
1999	9.796494886608187
2000	8.762251291713913
2001	7.090801820193963
2002	7.654777927321669
2003	5.3239320694669265
2004	4.965736225638699
2005	4.764412908226583
2006	4.741097357330825
2007	4.498248840448405
2008	4.027843192993311
2009	3.3022045423925914
2010	2.7698282305281237
2011	3.0339742208295233
2012	2.274509357349228
2013	2.02640198696812
2014	1.602104074938325
2015	1.4726667012397368
2016	1.3030997183234396
2017	1.1668992628455284
2018	1.2307629998974419
2019	1.0448107584373685
2020	0.6418763047659073
2021	0.5773880709456211
2022	1.4298922265147316