The One-Line Verdict
Amphenol distributed the additional shares on September 2, 2026 at exactly the declared two-for-one ratio. Nothing about the investment case changed. This event was plumbing, and the only thing that moved was the denominator under every per-share figure.
What Actually Happened
The board approved the split on August 5 and filed it as an 8-K Item 8.01 on August 6, 2026: one additional share for every share held at the close of business on August 17, distributable September 2. That is exactly what occurred. Amphenol's share count now stands at about 2.47 billion against about 1.233 billion before the distribution, and no amended or superseding 8-K has been filed since accession 0001104659-26-091969.
One detail is worth pinning down, because it is the most commonly misread part of a split. The distribution date and the date the stock begins trading on the halved basis are not the same day. This split is structured as a large stock dividend, so the exchange sets the ex-distribution date on the first business day after the payable date. OCC Information Memo #59532 records the full calendar: record date August 17, payable date September 2, ex-distribution date September 3, 2026. Amphenol therefore closed September 2 at $160.08, down 1.90% on the day, still on the pre-split basis, against an S&P 500 that closed up 0.46% at 7,666.60. The first session quoted near $80 is September 3, not September 2.
The Index-Weight Question
A durable retail belief holds that a split changes a company's index weight and therefore forces flows out of index funds. It does not, and the mechanism is documented rather than debatable. The corporate-actions table in S&P Dow Jones Indices' Index Mathematics Methodology gives the treatment for a stock split in one line: "Share count revised to reflect new count. Divisor adjustment is not required since the share count and price changes are offsetting." The divisor-adjustment column for that row reads "No."
The arithmetic follows directly. Amphenol's float-adjusted market capitalization before the distribution was about 1.233 billion shares at $160.08. After it, about 2.466 billion shares at $80.04. Both come to roughly $197 billion. The weight change attributable to the split alone is zero basis points. Any weight change observed over the coming weeks is a price move wearing a split's clothes.
The Hazard Nobody Prices
The real operational risk around a split is not the corporate action. It is the two or three days during which data vendors disagree about which basis they are quoting.
As of the September 2 close that disagreement was live and measurable. Nasdaq reported Amphenol's September 2 volume as 6,642,001 shares, the raw consolidated figure. Yahoo Finance's daily bar for the same session reported 12,656,626 shares, because Yahoo had already applied the two-for-one factor across its entire history ahead of the September 3 ex-date: prices divided by two, volumes multiplied by two. Yahoo's live quote field, meanwhile, still carried the raw $160.08. One vendor, two bases, one session. A third vendor was publishing a market capitalization of about $395 billion, which is the post-split share count multiplied by the pre-split price, roughly double the real figure.
None of this is a settlement error and none of it says anything about Amphenol. It is a reminder that any screen, backtest, alert threshold, or sizing rule that reads share volume or per-share price across September 2 and 3 will return a wrong answer unless the basis is pinned explicitly. A volume comparison is the sharpest trap: a two-for-one split mechanically doubles share volume, so a pre-split baseline drawn from a vendor that has already restated its history will silently compare doubled against doubled and show no change at all.
What This Changes in the Model
Nothing in the thesis. Earnings, cash flow, ownership, competitive position, and the CommScope CCS integration are all untouched by handing every holder a second share.
What changes is the units. Every per-share figure in the Amphenol file is stated on the pre-split basis and is wrong from the September 3 open until it is re-based: the price anchor, the scenario price targets, and the per-share earnings assumptions behind them. The quarterly dividend pays $0.125 on the post-split basis on October 14 rather than $0.25. Adjusted diluted EPS guidance for the third quarter is $0.70 to $0.71 post-split against the $1.40 to $1.42 originally guided. The October 21 third-quarter report is the first live check that the restatement has been applied consistently across the reported line items.
That re-basing is bookkeeping, and it has been queued as a maintenance work order rather than dressed up as a change of view.
The Honest Conclusion
This event changed nothing about the thesis. It was announced on August 6, the market had it from that morning, and it executed on schedule on September 2. Treat September 2 as the day the arithmetic changed and nothing else did. There is no incremental reason to initiate, add, or trim around it, and the lower per-share price is not itself a reason to buy.