Year	% of expense
1974	17.989036353144837
1975	18.48671231286991
1976	18.147351163029
1977	16.251830161054173
1978	15.388250118128838
1979	15.345688748685593
1980	15.7815223707147
1981	16.820147545153905
1982	16.588067321420848
1983	16.10506180105945
1984	14.922311057474733
1985	14.948793781927506
1986	16.849261769704913
1987	15.870372966909702
1988	15.509867186913784
1989	14.853269699431356
1990	13.888079277178663
1991	13.188100488265869
1992	12.37637529765526
1993	13.91196201100475
1994	13.581991083507154
1995	14.4662986771008
1996	12.570773930753564
1997	11.767313608837899
1998	11.955934300909355
1999	12.459273704487622
2000	11.557624368868739
2001	12.251367668836599
2002	11.622990068426393
2003	11.037013027316677
2004	13.041810191973092
2005	12.670510833947215
2006	11.182255948107251
2007	10.510535420660903
2008	9.76388479514927
2009	8.998098540350092
2010	9.392260808837534
2011	9.349227414920845
2012	9.42026100695438
2013	8.74170059547057
2014	8.498908372307834
2015	8.919965570395147
2016	7.750845738634429
2017	7.183137227567382
2018	6.686968800248626