Year	% of expense
1999	47.587804154525784
2000	52.4924781217681
2001	46.07718076033231
2002	43.83485492105956
2003	40.814666554341606
2004	26.670765260503725
2005	35.41328588693033
2006	34.66299896783566
2007	32.87854806373325
2008	33.555391184480385
2009	25.203445245210055
2010	26.39968411620879
2011	32.657654762669864
2012	35.460960746216074
2013	40.57508845551433
2014	34.23160268789525
2015	21.939215175274697
2016	21.533371562471896
2017	24.944872717116578
2018	21.464262211829517
2019	15.48482627581462