Year	% of expense
1972	5.767578844029952
1973	5.2093290001911585
1974	5.637874954824734
1975	5.929046833974488
1976	6.285454958021336
1977	5.501976868787652
1978	5.880019528866102
1979	7.7073824171462775
1980	9.014796380963421
1981	8.991472005932524
1982	4.220699978847693
1983	7.228996550827047
1984	10.56057802032768
1985	12.046471262328636
1986	13.824386385465386
1987	14.678559495810466
1988	16.025321530343597
1989	14.661185039466137
1990	20.869048435392855
1997	19.983966782462126
1998	18.28734858681023
1999	18.319204492613654
2000	15.884005287508263
2001	14.841596729738937
2002	13.580480699198835
2003	12.021814312317106
2004	11.258687258687258
2005	11.235259054943256
2006	10.751385041551247
2007	10.544287372806119
2008	10.539537489277524
2009	10.151675658807783
2010	12.008020524135999
2011	13.934440935840389
2012	9.434298357458937
2013	6.904219397699508
2014	8.335236094620512
2015	7.145041502839668
2016	6.933248853062997
2017	6.91722743238289
2018	7.319913300129127
2019	6.621861118143945
2020	5.346092963016261
2021	4.900052369989032
2022	5.164354930647919