Year	% of expense
1972	28.68452499502091
1973	27.915287888815353
1974	26.415223025508116
1975	25.606300002507965
1976	26.84937894781466
1977	28.73602949648577
1978	29.46600013242402
1979	30.09313154831199
1980	34.78049626930419
1981	36.4328557973529
1982	37.38486057211802
1983	35.48871801759452
1984	35.53513276553106
1985	36.6848183132108
1986	36.94658509733971
1987	36.70008934776134
1988	35.69540059440802
1989	34.73335833377977
1990	52.8416539966601
1991	58.390604687895156
1992	60.4409329312396
1993	59.04307812139613
1994	58.12490726231104
1995	52.43265725385907
1996	52.08633706252015
1997	51.57117181774225
1998	51.40397097567079
1999	51.6045314460845
2000	51.9006759024016
2001	51.380017698711136
2002	52.03981547096671
2003	52.79249573865774
2004	52.72315973379384
2005	52.16597604372163
2006	52.06511323033297
2007	51.507494942450904
2008	49.398653665899765
2009	51.51737597433993
2010	51.751241231121035
2011	51.81696794530504
2012	51.785024086276955
2013	52.6382156906281
2014	52.31575849402121
2015	52.91739632118374
2016	52.09255243006741
2017	50.2785472054674
2018	49.4624507984305
2019	49.85730513518493
2020	54.341685071404434
2021	50.37433829847321
2022	46.404753243603736