Year	% of revenue
1990	35.8915383869314
1991	34.482318988398106
1992	38.112150809370945
1993	35.842175066313
1994	38.38759836026952
1995	36.44566061457679
1996	34.83421370839432
1997	31.550360444377347
1998	31.40159968703096
1999	31.10169441950228
2000	31.226264279746317
2001	31.323921644039437
2002	31.35067562375253
2003	31.728416252278393
2004	31.112975467483317
2005	32.3216538641158
2006	28.60587854351563
2007	28.1825696002066
2008	27.61461607072552
2009	28.75832227800652
2010	29.741042800864026
2011	30.96397245868569
2012	29.091388850086187
2013	28.594850964690654
2014	28.218709202658854
2015	31.285220886915173
2016	32.93057846646643
2017	42.59794072705679
2018	47.756064579034025
2019	48.84418682877214
2020	41.59311052709953
2021	43.21569444177251