Year	% of expense
1990	9.822568029311267
1991	16.39746205244343
1992	17.47802654443801
1993	22.342038753159223
1994	33.25586354872545
1995	34.73270889737165
1996	48.80119189341393
1997	25.130973710689798
1998	11.861358263250693
1999	10.307153140381873
2000	11.86418965017437
2001	12.227377553575492
2002	6.55706429184751
2003	6.211182790830738
2004	5.377174013230195
2005	4.911018026972474
2006	4.3234589987506284
2007	3.370698914335684
2008	2.5767033756796294
2009	2.077612684811445
2010	2.113737577172073
2011	2.269562836099935
2012	2.4671309605840595
2013	2.22050631376707
2014	2.1743593695266634
2015	2.5863557087909355
2016	2.6485065520335844
2017	2.4276349955670575
2018	1.9059234596928278
2019	1.6013312745952912
2020	1.3642229440378522
2021	1.2138653952824454
2022	0.9310919145353459