Bad Day... Or Was It?

This year, and more specifically, this month, have had some prime examples of the impact massively weighted stocks can have on market cap weighted indices like the S&P 500. This morning, for example, the S&P 500 is down around 1.5%, yet breadth is modestly positive (+98 as of this writing), and while there is still plenty of day left for that to change, if it holds into the close, it will be the fourth session in a row with a decline on positive breadth or vice versa.  As shown below, that is the longest daily streak since late August and the sixth streak of at least four days this year. That includes the record 8-day streak observed at the end of June into the start of July.

In other words, 2026 has seen a lot of days where the S&P 500 has moved counter to what breadth would suggest. There have been 38 trading days where the S&P 500 has rallied on negative breadth (3 of which have occurred this month) and 33 where the index has fallen on positive breadth (6 of which have occurred this month). This week has been exemplary of that, and yesterday's session especially so. As shown in the chart below, yesterday's 0.3% decline came with +309 breadth. For all days since 1990, that is the S&P 500's best showing for breadth when the index has experienced a daily decline.