Year	% of expense
1997	31.353765255485396
1998	25.778122693298815
2008	50.411589662077816
2009	52.08755198947519
2010	50.10881718445058
2011	49.91191820931562
2012	51.19510181756102
2013	50.96321397161058
2014	48.1077585937789
2015	49.106626953214914
2016	50.43511916751934
2017	48.96056312908843
2018	46.39837173094771
2019	46.405917998399225
2020	50.27381553190599
2021	48.36463584390566
2022	39.11606956882503