BNN Bloomberg Sep 17, 2026 7 min
With Jonathan Corpina, senior managing partner at Meridian Equity Partners
Jonathan Corpina trades through the quarterly S&P rebalance for a living, and he said this one lands at tomorrow's close with a tremendous amount of volume behind it.
Most of the attention on air was on the Fed's quarter-point hike the day before. Corpina spent his time on the two mechanical events he thinks actually move prices this week: the rebalance, and the price of crude.
"But for now, we'll take oil sub-100 at this point, and hopefully we continue to see that downward trend."
Corpina is senior managing partner at Meridian Equity Partners, a floor brokerage whose clients are the institutions that have to trade the rebalance rather than read about it. BNN Bloomberg also asked him about the AI safety disclosures out of OpenAI and Anthropic.
The full segment is covered here so you can skip it.
Here are the 6 calls that matter.
Key Takeaways
Nobody was surprised by the hike; what Corpina took from the meeting was that the vote was unanimous and that the Fed gave a signal about the rest of the year
The sell-off was concentrated: the Dow moved far more than the Nasdaq, S&P and Russell, which are the indices his desk watches more closely
$100 is the line on crude — above it, volatility and fear; below it, calm — and he says the longer-term path is not forecastable right now
Tomorrow's close brings a tremendous amount of volume as the S&P indices add, delete and reweight names
The rebalance is a liquidity window that lets large portfolio managers move size without pushing the stock
He is not concerned by the AI safety headlines, because the warnings are coming from inside OpenAI and Anthropic rather than being forced on them
1. No Surprise, Unanimous
Corpina said the hike itself carried no news. What he took from the meeting was the voting record and the guidance, and he argued the market's positive reaction was about getting a plan rather than about liking the decision.
"I don't think there was a surprise to anybody in what occurred this week with the Fed." — Jonathan Corpina
"What was interesting that did come out of that is that a) it was a unanimous decision, and b) the Fed did indicate that there were more cuts likely to come this year." — Jonathan Corpina
"Whether you agree with it or not, having this information gives investors and traders a blueprint, a plan of what the next few months are going to look like." — Jonathan Corpina
2. Why the Dow Sold Off
The anchor put the change of heart to him directly: stocks fell after the announcement, then rallied the next morning. Corpina said the selling was not evenly spread, and that a policy statement takes a session to work through.
"So a little disconnect in the market yesterday." — Jonathan Corpina
"There's a lot more volatility in the Dow than there were in those other indices." — Jonathan Corpina
"And also, when this occurs, it does take a little time to kind of go through the transcripts, digest the information, see how overnight markets are going to react, see how oil is going to react." — Jonathan Corpina
3. Watching the $100 Level
Asked whether sentiment stays positive as long as crude falls, Corpina refused to put a horizon on it. He named a single price as the behavioral threshold and then described why the inputs change daily: shipping straits opening and closing, and barrel counts moving both ways.
"We continue to watch this $100 level." — Jonathan Corpina
"But the geopolitical risks and the geopolitical situation that we are involved in right now is certainly day-to-day." — Jonathan Corpina
"So unfortunately, it's very hard to gauge in a longer time frame what oil is going to do." — Jonathan Corpina
4. The Quarterly Rebalance
Corpina walked through the mechanics for the audience. Four times a year the S&P indices are reconstituted: mergers take names out, companies that no longer qualify are dropped, replacements are added, and the weight of every remaining name is reset to its price. The effect lands in a single closing auction.
"So what happens tomorrow, at the close of business tomorrow, is that we're going to see a tremendous amount of volume, potentially some volatility, and it gives portfolio managers — the larger portfolio managers — an avenue to get in and out of larger positions without having a substantial impact on the stock." — Jonathan Corpina
"But I also think it gives smaller investors the opportunity too, to look at their portfolios, see what stocks are in certain indices, and see if they're going to be added or deleted, because there will be price fluctuation due to that." — Jonathan Corpina
5. Tech's Forced Trim
The anchor asked whether the rebalance takes any air out of the top-heavy technology weighting. Corpina said it does, then argued against trading it. A stock being trimmed for index reasons is not a stock whose business has changed, and he would treat the selling as a chance to buy.
"So as tech has continued to rise over the quarter and the pricing of the individual stocks has gone higher, it has caused a larger impact, a larger movement, a larger weight on the S&P." — Jonathan Corpina
"It will have negative pressure on it, but overall the economics, the fundamentals of these companies, still remain very strong." — Jonathan Corpina
"So it actually might be an opportunity, if you do see some sell pressure on it, to act on it, because, you know, take a step back — these companies have performed very well over the quarters, and we're going to expect that to continue." — Jonathan Corpina
6. AI's Internal Warnings
BNN Bloomberg raised OpenAI's report of concerning model behavior and Anthropic's call to slow the pace of model progress, and asked whether that worried him. Corpina said the source of the warning is what reassures him, and he expects the regulatory response to be the hard part.
"Not concerned." — Jonathan Corpina
"I think our regulatory boards and our government are going to have a difficult time trying to come to some sort of consensus on how to reel this in, how to put some guidelines and some barriers on it, and the impact of that for some of these AI companies." — Jonathan Corpina
"They are raising the flag on this one themselves. They're not fighting against it. They're actually bringing this forward." — Jonathan Corpina
Bonus Insights
Corpina made a point about market structure that sat underneath several of his answers: the indices his desk follows most closely are the Nasdaq, the S&P and the Russell, and he treats the Dow as the noisier of the group.
He also separated two audiences for the rebalance. Large managers get an execution window; everyone else gets advance notice of which of their holdings are about to be added to or removed from an index, and therefore repriced.
Corpina's bottom line is that this week's price action is mechanical rather than fundamental, and that the crude price and tomorrow's closing auction will tell more about the next few sessions than the Fed statement will.
Products, Companies & Tools Mentioned
Meridian Equity Partners (Corpina's firm; he spoke as its senior managing partner)
S&P Dow Jones Indices (The S&P 500 and S&P 1500 rebalance he described, and the Dow he contrasted with them)
OpenAI and Anthropic (The two companies whose own safety disclosures he was asked about, and whose willingness to raise them is why he is not concerned)
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