Year	% of expense
1972	7.931034482758621
1973	12.939001848428836
1974	12.18274111675127
1975	9.152161706906233
1976	18.1850918257112
1977	11.361457334611696
1978	15.700787401574804
1979	15.835863284692978
1980	17.443172658391102
1981	16.500264596930673
1982	10.214825507344823
1983	14.133654202147353
1984	16.420967037600327
1985	15.014442013129104
1986	18.143740721263256
1987	19.65342119154668
1988	19.47076494669058
1989	14.178482068390325
1990	15.820394460763742
1991	16.679288148428626
1992	17.669982565890678
1993	13.940281030444964
1994	15.239706711787928
1995	12.752951096121418
1996	14.153142455029247
1997	12.859949292274628
1998	17.76591908848345
1999	18.29710900671645
2000	11.955647086100845
2001	13.505690872415627
2002	11.879040351005797
2003	12.937828672996021
2004	14.178443839636051
2005	14.446269940405735
2006	15.402759705474908
2007	15.504128572434334
2008	14.951724906303184
2009	12.446560821836933
2010	12.55872787732439
2011	11.77225685537563
2012	11.592290988326411
2013	11.762953498715657
2014	11.627908951378007
2015	11.710197170664033
2016	10.128351253329576
2017	10.76301425648254
2018	10.889938564116566
2019	11.063872576893036
2020	11.34857124743791