Year	% of expense
1991	0.3728560775540644
1992	6.515460156273751
1993	2.799966564061349
1994	3.461151277768492
1995	2.7533721473714414
1996	2.8322050600288047
1997	2.9173454345448984
1998	3.1545433703956376
1999	3.3380814935946073
2000	4.454409440173794
2001	5.058944843293927
2002	3.8420531540761935
2003	4.012110559685192
2004	4.290626869934304
2005	4.5488471072823
2006	4.424505414844936
2007	4.385314837759285
2008	4.531077087829621
2009	5.320174309283458
2010	5.6081060931394715
2011	6.130030494800908
2012	7.384343907913092
2013	7.481060314717203
2014	7.925070745468181
2015	8.071631805873269
2016	7.563168150165953
2017	6.66994629207666
2018	5.871115524021355
2019	5.606213932938903
2020	4.321490270039704
2021	3.66146582718099
2022	3.7860176593222405