Year	% of expense
1972	13.954033271561547
1973	10.591044057459273
1974	10.355806734060335
1975	10.16561568844848
1976	9.33232639619675
1977	8.885934358140405
1978	8.643145817770883
1979	8.038854738503009
1980	8.189697011717396
1981	7.952275613697209
1982	7.792616346329484
1983	7.682655148897477
1984	7.496892285359118
1985	7.73110324346264
1986	7.877553465524471
1987	8.427399645628398
1988	8.304930777572778
1989	8.085786775199535
1990	8.378028364761995
1991	8.38928852008249
1992	8.755034901925733
1993	8.606815945934386
1994	8.283808548682678
1995	6.402345201432469
1996	6.5567374614335945
1997	6.3984417635757795
1998	6.582209472878079
1999	7.109023738240067
2000	7.565708620774411
2001	7.929082193307958
2002	7.9202325518383905
2003	7.387831100967025
2004	7.619712441219284
2005	7.9742586349560804
2006	8.507246947194425
2007	7.569860239657496
2008	8.191163901799655
2009	8.100422534431296
2010	7.831179706657365
2011	7.872889182984953
2012	7.776545118365615
2013	7.917017038060344
2014	7.918841223427226
2015	7.743677664074757
2016	7.829524147367355
2017	8.105621390326908
2018	8.229396662852071
2019	8.353493119194283
2020	7.618182746443301
2021	8.116468960918517
2022	8.295721122520538