Year	% of expense
1972	62.79893711248893
1973	59.92808629644427
1974	50.9399636143117
1975	55.43026706231454
1976	49.29371651242085
1978	49.95131450827653
1979	45.03554792841383
1980	47.40113599828529
1981	50.41814760610496
1982	55.99207659293496
1983	50.14310246136233
1984	51.7670439816815
1985	43.82697685488189
1986	41.72406908255965
1987	42.81653066596473
1988	37.95091471270291
1989	41.235164957336224
1990	48.19054031307861
1991	38.56633432792373
1992	34.26124197002141
1993	31.729181410710073
1994	36.005210771642005
1995	41.25713317478472
1996	40.89144840643736
1997	43.40918116391352
1998	46.34203398177789
1999	44.31503212446238
2000	49.44983743882262
2001	48.296507497570424
2002	48.53052017651168
2003	45.159030085321696
2004	28.215429243301987
2005	34.43493950369382
2006	33.03829172839611
2007	34.4607137852003
2008	31.316669091185645
2009	35.683321998657455
2010	37.20639130663331
2011	36.77548558345221
2012	32.00288626819879
2013	37.98518991540269
2014	36.66898509317312
2015	38.52268196339985
2016	37.20904872306971
2017	37.93980210751231
2018	39.225304292987545
2019	39.137780141460645
2020	32.51826866777758
2021	35.81198094716551
2022	34.95936159521029