Year	% of expense
1988	2.375574735823185
1989	2.5509398199336566
1990	73.60139860139884
1991	75.80443555587296
1992	75.78233598915102
1993	74.9410300091731
1994	74.53734671125979
1995	74.79952011113215
1996	71.86627382093793
1997	72.39239653320345
1998	71.7754212478043
1999	72.73800207013204
2000	73.37648627290112
2001	72.58620497317075
2002	74.19897199404333
2003	75.48621913156637
2004	75.71848686690964
2005	75.80886404786271
2006	76.80703449085254
2007	77.27924703272132
2008	77.37504049471211
2009	77.26157426073334
2010	78.04581852694669
2011	78.28634838633057
2012	78.63416323432976
2013	77.37361863920997
2014	77.82633780470215
2015	78.52410236064273
2016	79.14134823581294
2017	79.38640810096102
2018	79.19690123545739
2019	79.14684312900852
2020	80.38021679899903
2021	79.90371325014495
2022	77.40028683794185