Year	% of expense
1990	64.03212885272168
1991	53.19016366204203
1992	50.92305208202516
1993	45.60248411489031
1994	46.879767022604355
1995	46.13600507018703
1996	40.328186286678914
2004	44.080918868901584
2005	42.17465313463515
2006	44.76546468457338
2007	44.561052512120945
2008	45.03239562683966
2009	42.46670113073636
2010	38.36679281532981
2011	36.72110217130049
2012	35.78827188750587
2013	32.22807198694359
2014	31.940142817992594
2015	31.184004888282995
2016	31.57710233589816
2017	31.18024921847778
2018	29.92287243511747
2019	30.93908030053913
2020	31.62419320701574
2021	29.07964078095538