Year	% of expense
1991	50.11631638055511
1992	52.618479726226276
1999	52.340247042147595
2000	51.715020510212305
2001	50.96526167265082
2002	48.76590034096056
2003	47.87883323646944
2004	49.82076688882003
2005	50.141712118766044
2006	47.84740078957604
2007	47.708273514401114
2008	42.29691221911501
2009	43.90155306809289
2010	45.848837082284646
2011	40.589213386534716
2012	41.12274233727304
2013	43.07960969784564
2014	43.227743024913075
2015	43.15693117583723
2016	47.76892662582235
2017	44.09100527501096
2018	46.130517544667164
2019	47.28819578113893
2020	42.1254978888658
2021	43.83127258826149
2022	42.85982762140334