Year	% of expense
1972	5.966587112171838
1973	5.297209866558836
1974	5.038759689922481
1975	3.8274012676743054
1976	3.8637851997380483
1977	3.681403750215035
1978	4.437518551498961
1979	5.809178743961352
1980	5.405985197897673
1981	5.887170154686078
1982	6.519961847663169
1983	6.798509601605045
1984	7.8728655618798165
1985	8.88112878108631
1986	9.704830053667262
1987	10.899297226781131
1988	10.415407854984894
1989	10.362880795785479
1990	10.908095947466027
1991	11.435832274459974
1992	11.53643222708806
1993	12.28625560591889
1994	12.476042300841057
1995	13.126240079365079
1996	14.128460976842577
1997	13.682731341729989
1998	12.448669447408413
1999	12.355047372065952
2000	12.054965646470956
2001	11.225978309126656
2002	10.835484405711986
2003	10.07677650126475
2004	9.879330323250889
2005	9.699809127190699
2006	9.551183964696634
2007	9.056288599757865
2008	7.564521895732086
2009	7.212575710347948
2010	6.514105413153744
2011	5.338710473310933
2012	5.098576759211386