Year	% of revenue
1997	91.02780112438418
1998	75.34662671206323
1999	74.25879517973539
2000	95.50052737558731
2001	96.04206770270905
2002	81.07290080588257
2003	79.9585807432815
2004	56.02759881719355
2005	49.74595102143509
2006	55.71839206421295
2007	55.956933227980386
2008	50.13873397585663
2009	48.69981967200899
2010	50.50476484300014
2011	42.95817981539864
2012	41.23185723028568
2013	43.66356154334054
2014	43.645799376845744
2015	50.42640774496512
2016	50.835470363174686
2017	45.69641562724066
2018	49.979757183491614
2019	50.825332413447754
2020	20.999779113121644
2021	13.590822335161759