Year	% of revenue
1972	28.940568475452196
1973	27.705779334500875
1974	27.49157438613385
1975	22.25867725781385
1976	20.904918032786885
1977	21.68415136755339
1978	21.612489805429334
1979	19.709085370497295
1980	18.205830561533947
1981	19.09924055984177
1982	17.62634381126711
1983	15.732154903328341
1984	15.901531117487242
1985	14.367181221162376
1986	12.773391567277004
1987	13.044307003037064
1988	9.967902187513305
1989	9.229879052299045
1990	9.08452693612581
1991	9.434552961983885
1992	8.37994194282148
1993	5.131383729575177
1994	1.4991642976197743
1995	1.3220652911778663
1996	1.2095798242005311
1997	1.1887921123906393
1998	1.2883094554368733
1999	1.1559994669103715
2000	1.1902232881185721
2001	1.2494618573191274
2002	0.9761715623730375
2003	0.9979110314273063
2004	1.0033829740921625
2005	0.8614031213872083
2006	0.9605048787863097
2007	1.0259752706233431
2008	0.9157119338252427
2009	0.9441808196566022
2010	1.104648462217007
2011	1.2365201842979734
2012	1.2102987213184695
2013	0.8711770578790101
2014	0.8198287093313797
2015	0.6628352080097747
2016	0.42033435505118955
2017	0.435691442223404
2018	0.435823529278165
2019	0.36982897556520505
2020	0.29658048763677597
2021	0.43301462071990887
2022	0.49211124075800194