Year	% of expense
1991	31.4134445692283
1992	28.45587472778181
1999	22.900575660273656
2000	21.402006597404764
2001	21.280518057608948
2002	21.318981698604617
2003	20.309424828465755
2004	17.9231830388015
2005	17.197821023971596
2006	17.613956933462173
2007	20.295710366273767
2008	20.60497482160329
2009	20.71215322625764
2010	17.436405337366605
2011	17.490890566925984
2012	16.23380989228731
2013	16.523390038523054
2014	17.292151296814744
2015	16.536601096318808
2016	14.374888436494029
2017	12.930079654176932
2018	10.329874401465188
2019	11.502519689756632
2020	13.124165440035531
2021	12.13969903222313
2022	12.041934227905864