Year	% of expense
1997	46.22884135940165
1998	44.03795955660284
1999	47.83534076729244
2000	46.5199396075888
2001	47.02698676092083
2003	50.29324730949879
2004	47.01508535580904
2005	49.36106249664478
2006	49.98143526263139
2007	44.2298798795201
2008	50.411589662077816
2009	52.08755198947519
2010	54.82306245736719
2011	50.83536171410594
2012	51.19510181756102
2013	50.96321397161058
2014	49.418765663561786
2015	48.12680260279123
2016	51.979203522099205
2017	48.96056312908843
2018	53.40208117939942
2019	53.03508047874536
2020	54.70065254812629
2021	49.82144676104734
2022	48.68888676929015