Year	% of expense
1998	25.929594212806734
1999	27.334511349734946
2000	24.17967224678482
2001	22.816609444840317
2002	22.173764323584745
2003	20.722687768718924
2004	23.32574297892217
2005	23.000835314452207
2006	20.077472200259923
2007	19.43558301730515
2008	19.116516446359494
2009	21.247276972758268
2010	21.234802000360546
2011	21.940283477253846
2012	22.235768471604427
2013	21.21513806941374
2014	22.026930822399333
2015	24.992854561201312
2016	22.39905985036986
2017	24.323890467389912
2018	23.048721532586626
2019	23.97524022224864
2020	31.91952952974723
2021	32.115479322911725