Year	% of expense
1973	3.1361368496079884
1974	2.9138915318744028
1975	2.680991095625229
1976	2.9752345532922027
1977	3.052567792758675
1978	3.1927257810897682
1979	3.331885586647644
1980	3.8363605499915123
1981	4.581746073161823
1982	5.575462233051453
1983	6.518478112641485
1984	7.476265822784836
1985	8.359906920623953
1986	8.768128021336866
1987	8.59721215051166
1988	8.768250383157218
1989	8.509714105196633
1990	8.634843417452176
1991	8.881825649083984
1992	9.021868113239567
1993	9.330362993054676
1994	9.259436215957935
1995	9.11283702721475
1996	9.931485278782832
1997	9.46229958833459
1998	9.312991997918157
1999	8.798061144631541
2000	7.592584772602508
2001	6.664361174016355
2002	6.037266550308775
2003	5.51946401520928
2004	5.4316953625738345
2005	5.1513422026293
2006	4.572148219033389
2007	4.525777082511798
2008	4.712969379846551
2009	4.377426303724268
2010	3.903281132646541
2011	3.9866690418930553
2012	3.7769214332554766
2013	3.53802506222019
2014	3.42420308668686
2015	3.1451191141728736
2016	2.855665966606782
2017	2.568815886598012
2018	2.262317691983079
2019	2.0105009988434444
2020	1.6064057438871804
2021	1.3519714876907392
2022	1.2883936282886657