Year	% of expense
2000	36.51348651348651
2001	30.664364784055532
2002	29.501838934285907
2003	30.027508196905895
2004	30.977364798045425
2005	32.59677944961808
2006	33.17294855175198
2007	31.468394189242243
2008	35.380954554792176
2009	34.40370445219465
2010	34.29663183308283
2011	36.8584835696031
2012	40.2991110702609
2013	35.42008896435889
2014	34.23965947704466
2015	38.10750371892738
2016	38.82375928096913
2017	38.39949816291782
2018	41.4096431862529
2019	40.622486290641554
2020	43.289365682091564