As far as I know, these are the estimates of the market size:
- The global e-Commerce market is worth US$7.7 trillion according to Statista.com (https://www.statista.com/study/44442/statista-report-b2b-e-commerce/ )
- 6.7 Tn by 2020 for the global B2B E-commerce market according to frost & Sullivan (http://www.frost.com/ma4e)
- The BIS Committee on the Global Financial System estimates that trade finance directly supports about one-third of global trade and that that, globally, a flow of some US$6.5–8 trillion of bank-intermediated trade finance was provided during 2011 (http://www.bis.org/publ/cgfs50.pdf)
HTH