Year	% of revenue
1981	29.85469616018368
1982	33.15703124103674
1983	31.31237372191269
1984	32.68598953112819
1990	25.801513072345752
1991	28.86358833530646
1992	33.54202648244099
1993	32.001414427157
1994	32.681335482484236
1995	30.838971197827057
1996	31.94121771789355
1997	30.429484985472037
1998	30.30855190398903
1999	32.25513038348585
2000	30.836011512053766
2001	31.609098045696815
2002	32.35269045443819
2003	32.766646778443594
2004	32.50597294092855
2005	32.41218974148977
2006	31.90915305893466
2007	31.68922429991976
2008	31.945694505915306
2009	33.6129591182516
2010	33.85075406743993
2011	33.40380917477158
2012	33.25940463706823
2013	32.9771450152989
2014	32.583097882547506
2015	32.3928751786495
2016	33.07345838229604
2017	31.880627997108395
2018	31.558151464837966
2019	31.49507147442008
2020	32.32417275533603
2021	31.78173335902038
2022	31.2683425396894