Year	% of expense
1991	11.520326906957251
1993	8.0039331366765
1994	8.397460386763449
1997	13.708891692887605
1998	18.78600850123044
1999	15.8823046643464
2010	0.8146414746234111
2011	0.4380795707295966
2012	1.5154549014444219
2013	0.2893034284498758
2014	6.396820642454715
2015	9.287043440352262
2017	4.5666272329358115
2019	4.328697463305101
2020	3.7464665185406156
2021	4.464757433131501