Will Baude ponders the 1787 decision to count slaves as 3/5 of a person and wonders why they settled on that particular fraction:
All of this just points to 3/5 being the result of bargaining; quite understandable, but also a little odd. After all, the highly natural focal point when two sides of roughly equal bargaining power are fighting between whether to pick 0 or 1 is 1/2. I can think of two possible explanations: Either some delegate (perhaps from North Carolina) was simply the first to name a middle-ish fraction, and everybody else realized that if they started dickering about the proper fraction, they were still going to get nowhere, or this is some evidence that the southern states had greater bargaining power than the northern ones, and thus could extract a little concession past the seemingly “fair” compromise. Neither seems greatly likely to me, but I am otherwise stumped.
I always wondered why they didn’t call it the “60 Percent Compromise.”
While I don’t know the answer to Will’s question and am too tired and/or lazy to Google it, I’m pretty sure it wasn’t greater Southern political pull. While everyone focuses on slaves counting as 3/5 for apportionment and thus representation in the House, the same figure also applied to the head tax that was the primary source of revenue for the federal government until the passage of the dastardly 16th Amendment and the income tax.
The other thing to keep in mind here is that it’s a misnomer to say that slaves were considered “3/5 of a person.” Indeed, as Dred Scott proved, they were in fact 0/5 of a person. The 3/5 was merely an accounting gimmick.
Update: Chris Lawrence proffers the possibility that the 3/5 formula balanced the voting power of the free and slave states. Hui Lun of Begging to Differ does the math and more or less confirms this theory.