Year	% of expense
1987	2.4605596312406672
1988	4.170403587443946
1989	5.645272601794341
1990	56.24036400556538
1991	57.01501877346683
1992	57.37031468155944
1993	59.14675437747896
1994	60.70352577151697
1995	62.8581448360512
1996	63.23687690273378
1997	63.89866689285664
1998	53.20046627554614
1999	54.932063702670305
2000	53.4190745785631
2001	55.82739492105881
2002	55.30242018634788
2003	54.359615211267965
2004	50.16837989464318
2005	51.77417076514503
2006	52.683184121630674
2007	61.45779203719497
2008	60.16926418509977
2009	56.93778132088624
2010	58.07694406809183
2011	58.587045510417504
2012	59.054401844684556
2013	62.48293529552021
2014	62.32472867472861
2015	61.84776092463016
2016	62.21502294359823
2017	63.30749804944582
2018	66.60426937832142
2019	69.09722462167734
2020	69.98748639287517
2021	70.07390889260554
2022	72.04032880087443