Year	% of expense
1972	11.563421828908554
1973	10.746147607461475
1974	10.25830258302583
1975	10.729312762973352
1976	13.188257631079306
1977	11.715904492108459
1978	11.401706208356686
1979	11.03537288750857
1980	12.503034062407291
1981	12.443600094989314
1987	24.71020752908439
1988	22.81716153406979
1989	21.035632844564372
1990	22.461997803977003
1991	21.76351759477417
1992	21.889343822409668
1993	22.377664619408446
1994	22.590874679255986
1995	22.731966271454375
1996	22.55732285319366
1997	23.09340575809745
1998	20.755154267989703
1999	22.742746238489865
2000	24.24833443474519
2001	23.860811467161458
2002	24.014957317973746
2003	23.251926901917148
2004	24.1225392345233
2005	22.87521876905185
2006	23.113698998329358
2007	22.828389301206826
2008	15.041777513341255
2009	18.87998775872523
2010	20.354764961507822
2011	20.082728033757938
2012	20.556155813396124
2013	20.54303062368374
2014	19.951754572665752
2015	20.26407574815957
2016	17.87164971776471
2017	20.488797256627322
2018	21.03990393288836
2019	21.165115252691397
2020	19.29645704513132
2021	20.92210843919425
2022	20.626793524426073