Year	% of expense
1990	3.5290009699320994
1991	4.177929662880447
1992	3.7093734562065737
1993	2.9857114785391548
1994	3.070086536212688
1995	3.236272938189773
1996	3.255521207954995
1997	3.143006074891103
1998	3.2051083454851264
1999	3.1294428313145475
2000	3.1689796020477243
2001	3.209726167391628
2002	3.3244668061494025
2003	3.297823610410454
2004	3.2931441010164244
2005	3.4161429333511273
2006	3.539578171431524
2007	3.5901855461751744
2008	3.579337713229695
2009	3.491741336312536
2010	3.5385469695778875
2011	3.74585347528886
2012	3.7623077313404156
2013	3.779059557736658
2014	3.854056475528593
2015	3.923653288081868
2016	4.01910603805543
2017	4.0238809662844615
2018	4.033826989230607
2019	4.039515887449791
2020	3.83760796624387
2021	4.108402292646047
2022	4.273673674902138