Year	% of expense
1972	18.27922077922077
1973	18.49493487698986
1974	17.771013814094978
1975	17.635733538698524
1976	17.522358396820117
1977	17.688164216043166
1978	17.096573208722713
1979	16.50129421915444
1980	20.65519156024427
1981	19.8169793909567
1982	19.37585510456707
1983	19.033075947908245
1984	18.821861710505555
1985	18.422461194102492
1986	17.91517488295238
1987	17.5513922043224
1988	17.10412963996042
1989	17.184297650953784
1990	17.163874131589683
1991	16.848505906879783
1992	16.67802550871384
1993	16.552755232806483
1994	16.460651009476717
1995	21.59583231879713
1996	21.82804817433048
1997	21.5381107193723
1998	21.875589228900346
1999	21.788767010400463
2000	21.90969599629826
2001	21.596188617507327
2002	21.32509800412998
2003	21.235766394155387
2004	21.03113228261597
2005	20.838584453980545
2006	20.50787127321976
2007	20.1110155605433
2008	19.561910306300884
2009	19.16553636722594
2010	18.471506541654474
2011	18.759181417753894
2012	18.588973609118682
2013	18.50639160812768
2014	18.425993645696263
2015	18.243032370849072
2016	18.19021473488872
2017	18.195776415716608
2018	18.291552998929976
2019	18.06330927711939
2020	17.427894930140937
2021	17.337213963070365
2022	17.435966721624716