Year	% of expense
1990	21.997295655411627
1991	48.19699684277486
1992	36.391359012458565
1993	30.1271604527666
1994	28.324768336415367
1995	25.363189193157627
1996	21.51404468624874
1997	21.26410652117766
1998	23.98106645439441
1999	23.131422568945084
2000	22.92232403114721
2001	21.820473051570378
2002	37.910946120852756
2003	36.26443226893706
2004	35.0160596051392
2005	34.45210199862164
2006	34.14035184414965
2007	36.013218285072064
2008	36.15647839704627
2009	38.909011106056006
2010	38.01429710197953
2011	36.42937746660226
2012	36.08939144238621
2013	37.10443392459204
2014	38.47259457521996
2015	37.10843044907691
2016	36.47347459537592
2017	37.41773759464635
2018	38.700248433994126
2019	39.90478026395445
2020	39.08353247689735
2021	34.23785284088084
2022	33.57319579941377