Year	% of expense
2000	15.35773205729697
2001	19.20741253280865
2002	17.62176968400854
2003	17.47085438752931
2004	17.039680115513843
2005	17.471830536469447
2006	18.675496024699072
2007	18.442526709594137
2008	20.09034665737107
2009	25.689548250933132
2010	27.870612640277116
2011	29.00637314690532
2012	26.82963822481415
2013	25.708816166376895
2014	24.03371912518913
2015	23.41976993565997
2016	23.072887317101607
2017	23.47367860754777