Year	% of expense
1981	13.490725126475548
1982	13.524027459954233
1983	11.672131147540982
1984	12.043189368770763
1985	11.77734375
1986	9.611248966087675
1987	11.800030025521693
1988	14.388777555110222
1989	13.3613074204947
1990	20.66365007541478
1991	8.991720188810648
1992	10.259831014547997
1993	12.569216708779098
1994	10.899922420480992
1995	7.761305777411807
1996	7.145766101681149
1997	7.540680436231819
1998	6.889331750596534
1999	7.632490725707998
2000	8.207666800398297
2001	8.108963281085396
2002	7.62860813455975
2003	7.896917295870558
2004	7.534257821820944
2005	7.422948925149308
2006	7.644827605521011
2007	8.136082059613182
2008	9.250278760390296
2009	9.692071786538582
2010	9.796572071662037
2011	9.102355065171427
2012	10.998503602077927
2013	11.167676325027227
2014	12.135962278406682
2015	13.101956233201264
2016	12.626798832771419
2017	14.31982206111822
2018	14.814803376673554
2019	15.88552852113217
2020	14.980476302606169
2021	15.55328317939556
2022	15.347987745898218