Year	% of expense
1972	15.465393794749405
1973	14.435907804286291
1974	10.942158616577222
1975	11.774744027303754
1976	11.26391617550753
1977	10.528126612764494
1978	11.63550014841199
1979	18.52657004830918
1980	15.585112088383568
1981	12.083712465878072
1982	14.150429213789344
1983	16.34852393235884
1984	11.519669571349418
1985	8.064744466990703
1986	8.922182468694096
1987	7.8525438707233945
1988	7.054380664652568
1989	7.143090867445437
1990	6.998449518134557
1991	7.482705068473811
1992	8.281010921753811
1993	8.084514473463319
1994	7.833322059121964
1995	7.368138227513228
1996	7.832712432371716
1997	6.425870025328753
1998	6.261519061014647
1999	5.821680640075442
2000	8.611465660049426
2001	8.517790321557683
2002	7.934496885878703
2003	7.682107397956341
2004	7.535861269828585
2005	7.20659013488954
2006	6.5128625654118295
2007	6.298560985701807
2008	6.0728047989194485
2009	6.394812275008098
2010	6.190096524114065
2011	5.0125830458597065
2012	4.3586999651304