Yams and sweet potatoes are easily confused and yet they are very different crops, including in global trade. Yams are starchier are more like potatoes, whereas sweet potatoes are sweet. Roughly the same volume of yams and sweet potatoes are produced by the world’s largest producers. Yet yams are mostly produced in Africa and consumed locally, whereas sweet potatoes also have roots in Asia and North America. 

Moreover, sweet potatoes have been a growing export business. The U.S. is the largest exporter, while China and Vietnam now compete against each other for the number two slot. Their exports have been more variable with Vietnam joining the fray more recently and pulling ahead of China in the most recently available data.&n...