There really isn't a strait answer here. As your question suggests, it really depends on where you are sailing, and possibly when. Are you sailing along the frequently traveled sea lanes like that one that goes north along the east coast of North America? Those had many vessels on it engaging in transporting goods. The best way to figure out if there will be a significant amount of vessels traveling in a particular area is to look at the economies of various islands/ports. What are they producing? If it's a crop with a growing season, when does that season come to fruition and thus the time to export? Where are the vessels that will pick up that cargo coming from? At this second, I can't think of a good mainstream book to read on the subject, but from a academic writing point of view, the works of Ralph Davis or Daniel Vickers both have excellent books and articles about Atlantic maritime commerce. I'm not sure there is a simple 1-paragraph answer I can provide, at least not that I can synthesize in my head right now.