Year	% of revenue
1976	2.2132023071993165
1977	1.9520063201553706
1978	2.0139549635267997
1979	1.5611722145337121
1980	0.9715647142547728
1981	2.024831264061328
2001	5.283028972312966
2002	5.68635615839881
2003	4.966219180486093
2004	4.660453338330812
2005	4.037000437395713
2006	3.5647572764956728
2007	3.9985033494750932
2008	3.740410019845137
2009	6.2702073803062035
2010	5.809109006247232
2012	5.711395974285692
2013	6.123641650527126
2014	6.15131626583083
2015	6.997529346130637
2016	9.637352435087692
2017	9.434820287094476
2018	9.893893156913887
2019	12.215073433878327