Year	% of expense
1990	28.91857179553044
1995	27.434699878913683
1996	32.602993365221415
1997	39.8505603985056
1998	29.68286205280425
1999	29.328621908127207
2009	29.53661844484629
2010	31.063148210657292
2011	27.595150723356838
2012	26.13195966848234
2013	26.40289892195225
2014	30.025974135479476
2015	30.50998770943473
2016	27.795954462508853
2017	31.931388586680026
2018	29.629466620427163
2019	31.98604636275056
2020	27.465045048071808
2021	28.214700987808598