Year	% of expense
1998	24.15850795519795
1999	22.445540661540953
2000	27.794581441505123
2003	28.196742690724136
2004	26.558922408497427
2006	27.877579629211887
2007	27.03167481084391
2008	26.707532476705303
2009	26.231989033158044
2010	22.799097139045713
2011	23.552351524001903
2012	24.985732539515315
2013	21.755151629901366
2014	21.596288748481523
2015	22.487062882233026
2016	21.50550970758002
2017	21.73025212496703
2018	22.00429834610583
2019	22.49290149281924
2020	21.227471552738688
2021	18.40959396427516
2022	21.897318404912586