Year	% of expense
1972	7.619639527656929
1973	7.30593607305936
1974	6.4737034331628935
1975	5.8447127119203115
1976	4.906139015728057
1977	6.231297306812181
1978	6.448855910803776
1979	7.034747388616499
1980	7.080630802492688
1981	7.15937264952503
1982	7.042941190830749
1983	6.97328764295446
1984	7.626219770895205
1985	9.090763000578518
1986	10.373109145062136
1987	10.822969758749574
1988	9.745600855636761
1989	9.14087075729201
1990	8.34078990587729
1991	6.435653854948345
1992	5.5571131628559
1993	4.8801377581839
1994	5.662601209388131
1995	6.484210526315789
1996	7.139118923744728
1997	7.254163616743512
1998	6.8076200783015555
1999	7.751632699944209
2000	6.568362085748556
2001	3.45060345060345
2002	2.8558961164025938
2003	2.4496696312658646
2004	1.9592689011823408
2005	1.812323461258732
2006	1.6806756452701619
2007	1.553144977726361
2008	1.4634945419565308
2009	1.4329316691677074
2010	2.0108004444202012
2011	2.7108523579290464
2012	3.313706381480593
2013	3.280155436637702
2014	3.260887683445768
2015	3.530981492770793
2016	3.613315957824902
2017	3.5648141225426215
2018	3.677479577031897
2019	3.5245419233334645
2020	2.962025232005017
2021	2.5710113330179563
2022	2.97349498522328