Samoa Exports of bitumen and asphalt (natural), bituminous or oil shale, tar sands to Tonga was US$206 during 2014, according to the United Nations COMTRADE database on international trade. Samoa Exports of bitumen and asphalt (natural), bituminous or oil shale, tar sands to Tonga - data, historical chart and statistics - was last updated on June of 2024.