Year	% of expense
1973	55.69620253164557
1974	54.2713567839196
1976	55.325443786982255
1977	51.05882352941177
1978	49.83870967741936
1979	50.815217391304344
1980	51.45413870246085
1981	52.75895450145208
1982	47.62492288710673
1983	41.3716814159292
1984	39.21568627450981
1985	39.86013986013986
1986	32.83731817421836
1987	38.48480681974426
1988	44.41433674097796
1989	45.42650602409638
1990	45.319031469358784
1991	43.69261108029826
1992	42.35219450275839
1993	40.92339183503279
1994	35.73521260590704
1995	38.27422270830078
1996	37.013820154697754
1997	37.36360015929908
1998	38.430510212341154
1999	39.009933958599255
2000	39.864447343383716
2001	39.1801030307085
2002	40.8851520226175
2003	42.85889947740547
2004	42.588446768526836
2005	41.41273760548922
2006	41.955337994594636
2007	41.6224940165751
2008	43.95833868127645
2009	45.57550778000496
2010	47.95046099621768
2011	49.155655802418316
2012	47.66048401861842
2013	47.52125233257309
2014	46.22778118488793
2015	43.41311569593543
2016	45.15479334532761
2017	46.93211197450098
2018	41.38343524675063
2019	39.76525575595117
2020	38.50258457790506
2021	38.14206323480377
2022	37.85998834878457