Year	% of revenue
2001	15.462607193656414
2002	16.478572801315693
2003	16.68044829007181
2004	16.37309900324118
2005	16.89407012073786
2006	19.08373772053146
2007	20.695097077119144
2008	21.810102094877013
2009	21.728633024742336
2010	18.305351091755984
2011	15.862255573481256
2012	16.74448339016497
2013	17.17622912831816
2014	18.437065115033647
2015	20.42658856406509
2016	18.459081568837664
2017	18.700454630297514
2018	18.07224020641442
2019	19.040035892135332
2020	21.09036423540087
2021	20.82773840405256