Year	% of expense
1982	38.12206572769953
1983	34.9628982976866
1984	29.925105828720287
1988	43.4523098961442
1989	51.77304964539007
1990	47.86396070799741
1991	47.44473283809183
1992	43.334178713331646
1993	39.77987421383648
1994	31.019050498941642
1995	30.96764423804957
1996	25.699434337257298
1997	34.77393871994478
1998	40.555252336448596
1999	37.64626600502359
2000	42.41647959857388
2001	37.971084762198615
2002	39.30152091695863
2003	36.235421984294405
2004	38.57788761434351
2005	37.17788402977043
2006	39.40285329895173
2007	39.539937400972306
2008	31.597954752625775
2009	35.01013184372903
2010	38.07506028647707
2011	37.913082757590445
2012	38.04416125953748
2013	37.47240407236483
2014	38.08966656583962
2015	39.9331848756106
2016	36.18865744063263
2017	33.790357425751
2018	30.461946779736575
2019	38.77400507498015
2020	40.384061598368405