Year	% of expense
1990	61.96603332984237
1991	62.71227334328927
1992	63.54381648090895
1993	63.24703800200915
1994	62.90455323976241
1995	55.32083902031354
1996	56.618661789036835
1997	57.83621035772654
1998	54.25928619762087
1999	56.38468298807282
2000	55.62927093977633
2001	58.115922312473955
2002	58.378065785853195
2003	59.95598772014337
2004	59.5203833935538
2005	59.22539330106267
2006	59.500667862721386
2007	59.774174299183855
2008	59.98688576732765
2009	60.148137404963926
2010	61.22654252889939
2011	60.363925530096246
2012	62.38716038509109
2013	63.435900657454326
2014	64.21416248197444
2015	64.29134614310624
2016	62.21502294359823
2017	63.15631478291337
2018	61.69625347681487
2019	64.60094387735931
2020	61.09167579734651
2021	63.02244585869781
2022	62.47015805575518