Year	% of expense
1980	11.069651741293532
1981	15.922920892494929
1982	11.615700593336376
1983	11.212965679084776
1984	12.660173512067512
1985	10.304014617063391
1986	7.172607717272079
1987	8.225186104218363
1988	8.049749724076918
1989	6.412194567133622
1990	38.02167821155703
1991	38.56848294306188
1992	39.03781870616766
1993	40.16083758719932
1994	43.08980502395934
1995	45.5498577356737
1996	46.679838384390834
1997	49.462166515468496
1998	49.983541895638886
1999	50.8039396388836
2000	37.0808813110062
2001	38.23695234569777
2002	35.58266112994603
2003	37.746181877158655
2004	36.83599708153772
2005	36.33352361238269
2006	36.29314464561913
2007	36.81467094129351
2008	36.417995074092595
2009	36.63451932107898
2010	38.12816805696873
2011	38.575754671729584
2012	38.94503357488999
2013	39.33070954163853
2014	40.527977019594424
2015	41.026930152130326
2016	41.42550481007511
2017	42.1984428885335
2018	42.57367998591633
2019	43.455577775939076
2020	49.63506374560692
2021	46.148609277242635
2022	41.95996047796536