Year	% of expense
1972	2.3458191449110855
1973	2.1119258005890766
1974	2.064944971123454
1975	2.3221525985993328
1976	3.311720288903472
1977	3.815110978252751
1978	4.37334032718094
1979	4.690915715326679
1980	4.969468441342817
1981	5.278232405891957
1982	5.983408145519498
1983	5.9065844249253585
1984	6.9549104385423
1985	7.525113082300415
1986	7.785293635021063
1987	8.546786961180809
1988	8.69025247160715
1989	9.23702433136395
1990	9.591176295944432
1991	10.007383504703558
1992	10.014237046829715
1993	9.733987392656985
1994	9.292212558667169
1995	7.977165759191901
1996	7.958875536892659
1997	7.592787881207072
1998	7.462856934674618
1999	7.213367540189706
2000	7.5079701019353395
2001	7.282187919051782
2002	7.272568019903149
2003	6.814471247040369
2004	6.199583287492241
2005	6.927045931274667
2006	6.720004508168039
2007	6.72938760368424
2008	6.140727030982767
2009	6.29971546386008
2010	6.0578981516118935
2011	5.94325696200971
2012	5.777536577835267
2013	5.446249074329694
2014	5.0039956185322385
2015	4.928273334269164
2016	4.528591016908115
2017	4.096380980067511
2018	3.644301750481034
2019	3.2504941336928486
2020	2.6905526145529097
2021	2.264924119158397
2022	2.030800801795448