Year	% of expense
1998	29.45142506723154
1999	28.896163713808814
2000	30.469046806038396
2003	32.52382014925004
2004	35.58211169898131
2005	27.638669058843796
2006	32.03155162982382
2007	29.534038153397734
2008	35.67991237173165
2009	30.407293810539997
2010	31.647235226508986
2011	31.817824322063625
2012	32.59447441412772
2013	29.48726709021469
2014	32.34877497087901
2015	33.79859732709892
2016	34.15864105225786
2017	34.23438856401272
2018	33.48883427161306
2019	37.34020415993059
2020	34.789580875124976
2021	36.77375038660633
2022	35.268740469112025