Year	% of expense
1998	41.97097918985321
1999	38.77631997275407
2000	40.813965070507074
2001	42.97618875075959
2002	40.53068859354806
2003	36.90702218710451
2004	36.99194710330269
2005	37.55632961615654
2006	38.81360245001757
2007	39.171459880232085
2008	40.35904894591047
2009	41.35578318319796
2010	41.82989584777705
2011	44.41946145066542
2012	44.35963357121388
2013	44.557449620571624
2014	42.47643544926623
2015	41.964080385160344
2016	43.356434958846854
2017	40.956031477639
2018	41.25498932314408
2019	42.47677806413792
2020	47.12252391192138
2021	45.863953340387134
2022	39.77743210603805