Earlier quoted context omitted.
> Isn't that example nearly zero-sum (ignoring the spread)? But ignoring the spread is incorrect, and nearly zero sum is not the same as zero-sum. The spread is the fee that market makers earn for a service they provide. You're also not considering other participants. The price changes you're talking about could be driven entirely by end users, or they could be driven by speculators, arbitrageurs, and others who are…
Are you saying that the "misconception" is that it's actually slightly negative-sum, rather than exactly-zero sum? If so, great, I agree. It doesn't change my point at all; if anything it makes it stronger. I am not excluding anyone; I'm trying to explain why I think the result here is not particularly enlightening.
> Thus, any analysis that averages across market participants' P&L will conclude that futures trading is unprofitable[0], except for the market makers. This is true regardless of the savvy of market participants.
By virtue of offering various services to market participants, savvy market operators can consistently generate profit. In the context of this article, I took your statement to mean that any given participant cannot consistently do so.
At the same time, the end users entering into these transactions understand they will be paying these fees, just as a firm expects to pay a fee to borrow money from a bank. If we describe this process as a zero-sum game, it gives the impression that trading is a speculative casino, reallocating money to participants at random (the misconception). If we describe it instead as negative-sum, where participants are paying/paid for services, it better reflects the economic value of the transactions.
> ignoring/averaging across trades with non-daytraders
I didn't see this bit for some reason when originally responding to your comment. Had I, my comment would have been stated differently.