Year	% of expense
1998	16.416442367078666
1999	11.496299247399513
2000	9.686458392181233
2001	29.103604721227804
2002	3.1472081218274077
2003	4.1704758173349
2004	4.698235840297118
2005	24.588802126599102
2006	23.289039309789995
2007	20.923710868196647
2008	21.166581140190114
2009	20.986243572276184
2010	22.465427442528735
2011	24.892420794845798
2012	24.394804681802405
2013	14.656911212181134
2014	27.70527834608577
2015	28.46933288346989
2016	21.579290649990593
2017	19.42868399678214
2018	17.744241708370893
2019	19.72774806178256
2020	28.606047710239498
2021	21.806555502397927