Year	% of expense
1998	22.63837314809873
1999	21.46249758781895
2000	21.44624597480368
2001	17.562825647751037
2002	15.013666536509177
2003	14.58360541552392
2004	13.441039925719592
2005	18.3884366173783
2006	16.065137182012375
2007	15.821553253591256
2008	16.509053588446594
2009	14.903529204940009
2010	16.837284482758623
2011	13.031317338206108
2012	16.587431410604545
2013	16.810361874629226
2014	17.723505004878575
2015	15.999444788735385
2016	15.949852237105656
2017	15.924067452927313
2018	15.902520903919678
2019	15.42460484404111
2020	11.397971487339529
2021	13.787792156267868