Year	% of expense
1990	27.110574049872298
1991	25.951323702995904
1992	23.36525834926203
1993	21.14294009937387
1994	19.489163519014234
1995	49.15908521826225
1996	50.28359511343804
1997	51.56120598965911
1998	51.744108934966185
1999	51.60503421626406
2000	51.295851976741666
2001	50.8898498898083
2002	50.872269864008324
2003	51.04241417078974
2004	51.03512317692685
2005	50.49981617968873
2006	50.04555578052238
2007	49.72240873880218
2008	49.158529625001925
2009	49.97840794587592
2010	50.32887904175033
2011	50.214643771331055
2012	50.90539399984655
2013	51.34778786990917
2014	52.36466353603013
2015	53.10060736562474
2016	53.17817033088278
2017	54.51365406590332
2018	54.10202095379859
2019	54.078070096405085
2020	53.39593241743133
2021	52.700134056303646
2022	51.451265243452326