Year	% of revenue
1995	15.001969034344103
1996	20.765854074548848
1997	17.074716647685413
1998	12.421467204710805
2002	16.555809955045387
2003	16.936107774462375
2004	17.55432279548427
2011	17.01498577433315
2012	17.572697432454596
2013	18.818148522294912
2014	19.469350534172396
2015	18.909627864662067
2016	20.565196456809993
2017	20.742613833507516
2018	21.38657226615747
2019	22.195218076720966
2020	23.839939176243135
2021	19.688460620992082