Year	% of expense
1990	22.348374575448812
1991	19.275575134605972
1992	18.671519563239308
1993	26.481796805319064
2000	29.515418502202646
2001	25.895765472312704
2002	22.18971205923604
2003	21.257490523318324
2004	23.11977619193069
2005	21.498565837864927
2006	21.807255535998816
2007	19.72183674698874
2008	25.585393189306348
2009	23.679000179760028
2010	22.275248047685515
2011	29.597256774020035
2012	23.64491454086301
2013	28.304613079310712
2014	25.667288397221505
2015	26.179182516946103
2016	7.967775911639956
2017	22.8203717290291
2020	28.32080200501253