Year	% of expense
1990	52.7609756097561
1991	52.13233181463694
1992	51.36151130617308
1993	44.956433506740325
1994	44.31979657467654
1995	42.546504941358975
1997	44.08159647478917
1998	44.52266503696217
1999	45.37263252269416
2002	47.32226471741371
2003	50.962685420297774
2004	49.60846904093955
2005	44.3251187120407
2006	48.20765048765528
2007	46.183722338302935
2008	43.1956910439349
2009	47.39563604258098
2010	41.69087628106614
2011	41.24874873663962
2012	43.12362392750077
2013	45.10314020444048
2014	46.086684248717
2015	47.54308569516307
2016	48.41236257275068
2017	46.7855871854314
2018	45.5802968491594
2019	45.312108524760504
2020	42.5805629909583
2021	42.9274490162232
2022	39.36743689153197