Year	% of expense
1973	38.769716088328074
1974	34.07518234524032
1975	32.15130023640662
1976	36.871829233272706
1977	38.31833217939842
1978	38.31563956499223
1979	39.45065373260228
1980	36.039529055747316
1981	33.74451021577239
1982	35.708651064948725
1983	38.15198932557011
1984	36.967274400414105
1985	35.1492694207926
1986	35.624534392848275
1987	36.10714050095661
1988	39.67631365065903
1989	44.587760404584046
1990	44.75668449197861
1991	41.35690956727721
1992	40.3393351800554
1993	40.38547203991328
1994	45.190152872078976
1995	45.0312271083018
1996	42.014021669853406
1997	39.86026390780393
1998	39.440229649374615
1999	37.76353516613257
2000	38.24354543606424
2001	37.0948330299766
2002	38.25343304907216
2003	37.318871255522836
2004	38.197038521181845
2005	39.023309334618794
2006	36.26652111193419
2007	35.41206533463455
2008	33.826848389443846
2009	35.718456940675345
2010	35.23337457766347
2011	36.42901618929017
2012	35.952153458619016
2013	37.79974632869161
2014	37.352512354057325
2015	34.52192194061008
2016	34.76563861188499
2017	36.13904743112097
2018	34.43517324763137
2019	34.25163473689054
2020	29.095548149627515
2021	26.89995162468824
2022	30.681773097851924