Year	% of expense
1972	16.580362477594104
1973	16.024707699095522
1974	16.450688855544946
1975	16.086073282672487
1976	15.585654330408241
1977	14.369935092368552
1978	13.763821757266767
1979	13.528209205258527
1980	14.086413326392504
1981	13.475437465919793
1982	12.89741673494746
1983	13.101034181720502
1984	12.606462925851702
1985	12.523176197497701
1986	12.603993924107082
1987	15.294351235977366
1988	15.741716463587776
1989	16.350291969499455
1990	15.111786844794498
1991	14.041057904334284
1992	12.84104518021098
1993	11.235929565588926
1994	8.799675734753924
1995	15.470004946922982
1996	15.471258494089879
1997	15.851303557146377
1998	15.61985782199785
1999	15.249664922270503
2000	15.05866875456061
2001	15.774420037578066
2002	15.480352726402389
2003	15.359532617270204
2004	15.650619565546704
2005	15.430939278668717
2006	15.659699833636727
2007	15.50549382060987
2008	14.525587651706045
2009	14.51530642327331
2010	14.071040944433962
2011	14.459121038235203
2012	14.56866238675679
2013	12.704211230413248
2014	13.128127009733925
2015	13.117898594990837
2016	13.442369721779288
2017	15.179010587900283
2018	15.718748413601485
2019	16.26904479240002
2020	14.350939459064197
2021	15.124248669586866
2022	15.437252773377864