Year	% of expense
1997	36.85862679070829
1998	36.78571428571429
1999	35.99958394008737
2011	29.66687010926651
2012	31.08602655269476
2013	32.226993256437495
2014	34.26731692817205
2015	36.66984471631688
2016	34.824279729047774
2017	37.278347426104546
2018	35.57200096487209
2019	34.465191214115166
2020	34.30027827719143
2021	33.074886753359934
2022	30.206541498308546