Year	% of expense
1997	9.46527843211156
1998	11.979003907088588
1999	8.327711925875317
2000	9.827238417842008
2001	8.414607284848078
2003	6.620457120135793
2004	5.05970683245881
2005	4.08486966035415
2006	3.058075068541489
2007	1.9747737835313264
2008	2.0250695928011915
2009	2.220836306804108
2010	2.576051629810144
2011	3.285260004725467
2012	3.819662797644034
2013	3.2494648587259785
2014	3.3184031249070474
2015	4.073929534907986
2016	4.273063120379516
2017	4.291837763849866
2018	4.4885220079923
2019	3.9397854054038604
2020	3.750544628604583
2021	4.111040521925601
2022	3.8748087882081026