Year	% of expense
1990	32.759867228954334
1991	32.54439195324594
1992	33.833663747656054
1993	33.26952812123199
1994	32.14675727522237
1995	32.351748748024
1996	33.400030054138064
1997	34.10366821569103
1998	21.70962660005661
1999	21.672098199224184
2000	21.885229682793387
2001	26.26894200992548
2002	26.782380147395816
2003	28.601471930971968
2004	28.569443771202145
2005	25.62919065346939
2006	24.232706924035735
2007	24.84755673868596
2008	16.215601197762602
2009	24.174891054751985
2010	25.517945448401274
2011	26.518988756622452
2012	25.797387174830472
2013	26.09493437180323
2014	25.742672974272125
2015	25.21597601125094
2016	22.716118100905074
2017	27.55585474634695
2018	28.608063095409374
2019	30.489155915799437
2020	35.475940557561955
2021	34.08912069931989
2022	30.052775622665877