Year	% of revenue
1998	26.949006050129647
1999	29.697417772245238
2003	30.19880227637347
2004	27.01329271539342
2005	30.495367399540676
2006	31.247044383053765
2007	30.286773370334387
2008	28.907023705550344
2009	33.00847088407046
2010	30.305574483273308
2011	28.939807842592234
2012	27.89918637889472
2013	28.03921789275437
2014	26.486696593715877
2015	24.72014267952282
2016	26.47794457443528
2017	24.916666870461377
2018	24.847705592324978
2019	26.956995416309653
2020	28.178882852005323
2021	26.933803764524605
2022	27.774211775272583