Year	% of expense
1972	4.625529910504004
1973	4.856225145304374
1974	4.726752503576538
1975	5.765240588874617
1976	7.527873250062872
1977	9.116727181220117
1978	10.232927313246023
1979	11.828680647158587
1980	14.121760096443642
1981	15.844906121542051
1982	16.73978932197283
1983	18.995557899434086
1984	20.422144780611436
1985	21.18124333384123
1986	21.449076732168983
1987	21.435584160575978
1988	21.097318595487987
1989	19.64508635810565
1990	20.48002254509018
1994	15.197658652474788
1995	14.734162679425838
1996	14.504581472266354
1997	14.60519740129935
1998	10.724085175153201
1999	12.352538353155328
2000	11.887659975809866
2001	11.364513269722092
2002	10.631039287105178
2003	10.125702221629034
2004	9.924486783307394
2005	9.435158084373214
2006	10.292292549321692
2007	11.498426242619495
2008	10.862960039320237
2009	9.252723918226428
2010	9.68870174084437
2011	9.22219579693851
2012	9.340555687327969
2013	9.260134197933283
2014	9.457350397634483
2015	9.469497880093906
2016	9.33075812822015
2017	9.08943744759808
2018	8.93650413938192
2019	8.501954039421285
2020	5.926917935163591
2021	6.156772123155515
2022	6.260537365134512