Three Memory Chip Companies Account for a Quarter of S&P 500 Gains
0xBroomberg
In the first half of 2026, Micron, SanDisk, and Western Digital together drove nearly a quarter of the S&P 500's total gain, replacing Nvidia and peers as the market's structural engine — but the earnings-upgrade momentum behind the rally is fading.
How did three companies carry a quarter of the index?
Bloomberg strategist Simon White calculates the S&P 500 rose 8.3% over six months. Micron alone contributed about 1.4 percentage points — roughly one-sixth.
Add SanDisk and Western Digital, and the three account for close to a quarter of the index's total gain.
This means → in a 500-company index, nearly a quarter of the upside concentrated in just three memory-chip stocks — an extreme level of concentration.
How did memory stocks take the baton from Nvidia?
In early April, a clear split emerged inside the AI trade: the gap widened between hyperscale cloud operators (the big buyers like Amazon AWS and Microsoft Azure) and chip-hardware companies.
Within hardware, memory-chip makers pulled ahead of processor-chip makers, opening a second layer of divergence.
In plain terms = the AI rally used to be led by Nvidia, Apple, and Alphabet. Now the lead has passed to the companies that "store AI's data."
How much is left of the "upgrade cycle" that powered the rally?
The fundamental driver was a synchronized, sharp upgrade in earnings expectations. But according to White, the ratio of analyst upgrades to downgrades for next-year earnings among S&P 500 constituents has fallen back to 1:1.
The upgrade-to-downgrade ratio for earnings two to three years out is declining fast.
This means → the "expectations keep rising" tailwind is largely spent. From here, share prices need real earnings to hold up.
What is the biggest risk for the second half?
To sustain current prices, memory companies must deliver actual results that match already fully priced-in expectations — if they miss, the downside is material.
Memory stocks have already pulled back in recent sessions, though that does not erase their outsized first-half contribution to the index.
In plain terms = the first half was powered by "the market keeps getting more optimistic." The second half requires "the companies actually earn it" — a shift from trading on expectations to proving them, which is a fundamentally different game.
Content is for reference only, not financial advice.