Year	% of expense
2001	26.49868061538354
2002	25.29284704452421
2003	28.53286513723291
2004	29.45341723620632
2005	30.611836788176973
2006	29.04596538646193
2007	29.319570552628605
2008	31.472154993817515
2009	34.871885308657504
2010	35.977748502436775
2011	34.40081337164888
2012	35.5887568364776
2013	36.67058069857047
2014	32.62346772357212
2015	31.769534868916814
2016	34.10061451932091
2017	33.48432753303338
2018	33.69491379402746
2019	36.1846741049808
2020	36.00294185956491
2021	34.12039334284496