Year	% of expense
1972	23.543369364619032
1973	27.015144113336564
1974	21.802377150966763
1975	18.7451103113754
1976	18.806689342403672
1977	22.095448411237896
1978	15.842940303618262
1980	10.27493666134937
1981	12.672605790645864
1982	14.098039215686272
1983	12.296564195298371
1984	11.220029142932848
1985	10.484876320451406
1986	3.6133181990162777
1987	6.547374596655914
1988	8.211096075778075
1989	8.925049309664699
1990	11.793819949168403
1991	15.181713924150756
1992	14.809253101648256
1993	13.59004853588763
1994	13.270183619935871
1995	12.161206945248088
1996	11.119217387270346
1997	11.274716159882757
1998	10.628825684509152
1999	10.208147285547915
2000	11.487878605119818
2001	10.008837968067088
2002	10.47281597352897
2003	10.19313432720754
2004	11.64502610085925
2005	10.678834106883189
2006	12.324722000949913
2007	12.163452352574733
2008	13.99942791471284
2009	12.970071725013838
2010	13.855007472899322
2011	14.084066643686329
2012	14.859066628448916
2013	13.757293013346702
2014	14.242984171500103
2015	15.267711988926802
2016	15.597129387713604
2017	16.742999269973076
2018	17.463201099561886
2019	18.971817385148512
2020	19.700397642836677
2021	19.97170057893854
2022	19.348418391078674