Sandisk and Western Digital Beat Earnings — So Why Did Their Stocks Fall?

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Sandisk and Western Digital both reported strong quarterly results.

Revenue beat expectations.

Guidance was also above formal analyst consensus.

Yet both stocks fell sharply.

That is not a contradiction.

It is a reminder that stocks trade against expectations, not just reported results.

Bottom Line

Sandisk and Western Digital delivered strong operating results.

But both stocks had already risen dramatically on expectations of:

  • strong AI-related storage demand
  • continued price increases
  • margin expansion
  • repeated earnings upgrades

So simply beating consensus was no longer enough.

The key distinction is:

Good results ≠ positive stock reaction

What matters is:

Reported results vs. what the market had already priced in

Claim

If a company beats earnings expectations, its stock should rise.

Verdict

MISLEADING

An earnings beat can still produce a negative stock reaction when expectations embedded in the share price are higher than published analyst estimates.

That appears to be what happened here.

3 Key Facts

1. Sandisk Reported Very Strong Growth

Sandisk reported fiscal fourth-quarter revenue of:

$8.965 billion

up:

51% sequentially

Full-year fiscal 2026 revenue reached:

$20.248 billion

up:

175% year over year

Its data-center revenue rose:

437% year over year

For the next quarter, Sandisk guided to:

$10.3B–$10.8B

of revenue.

These were not weak results.

2. Western Digital Also Beat Expectations

Western Digital reported fiscal fourth-quarter revenue of:

$3.747 billion

up:

44% year over year

Non-GAAP diluted EPS reached:

$3.56

For the next quarter, the company guided to approximately:

$4.1 billion ± $100 million

of revenue.

Again, this was not an earnings miss.

3. The Stocks Had Already Priced in a Lot of Good News

Reuters noted that both companies had dramatically outperformed the broader semiconductor market before earnings.

That created a much higher hurdle.

Sandisk and Western Digital both issued forecasts above LSEG consensus estimates.

But those forecasts still fell short of the more aggressive expectations investors had built into the stocks.

Why an Earnings Beat Can Still Disappoint

There are at least three different benchmarks.

1. Company Guidance

Did the company beat its own previous forecast?

2. Analyst Consensus

Did reported results beat published estimates?

3. Market-Implied Expectation

Was the result better than what investors had already priced into the stock?

The first two are observable.

The third is not directly visible.

That is why a stock can:

beat earnings and still fall

The market may already have expected:

  • even faster revenue growth
  • stronger pricing
  • wider margins
  • a larger guidance raise

Sandisk’s 437% Data-Center Growth Needs Context

Sandisk’s fiscal 2026 data-center revenue rose:

437%

That is a major growth rate.

But it should not be interpreted as:

  • 437% growth in HBM
  • 437% growth in total AI memory
  • 437% growth in the entire data-center storage market

It is specifically Sandisk’s data-center revenue.

The company also said roughly:

  • one-third of sequential revenue growth came from volume
  • two-thirds came from higher pricing

That distinction matters.

Pricing can improve earnings rapidly during a tight market.

But pricing gains can also normalize later even if demand remains healthy.

Why Pricing Expectations Matter

Investors were not only asking:

Is demand strong?

They were increasingly asking:

Can pricing, margins, and growth keep improving faster than expected?

That is a much harder test.

A company can still grow while its stock falls if:

  • price increases slow
  • margins stop expanding
  • guidance stops being revised upward
  • valuation already assumes exceptional growth

This is the expectation gap.

Sandisk and Western Digital Are Different Businesses

They should not be treated as the same “AI memory stock.”

Sandisk

Primary exposure:

  • NAND flash
  • enterprise SSDs
  • data-center storage

Western Digital

Primary exposure:

  • high-capacity HDDs
  • large-scale storage

Western Digital completed the separation of its flash business into Sandisk in 2025.

So Sandisk’s NAND pricing and Western Digital’s HDD shipments are not interchangeable indicators.

Both can benefit from AI data-center growth.

But they benefit through different parts of the infrastructure stack.

Why This Matters for SK Hynix and Samsung

The selloff in Sandisk and Western Digital does not prove that HBM demand weakened.

That is an important distinction.

AI data centers use multiple layers of memory and storage:

  • HBM
  • server DRAM
  • NAND / SSD
  • HDD

Those markets are connected to AI infrastructure spending.

But they have different:

  • supply conditions
  • pricing cycles
  • customers
  • production constraints

So:

Weak storage-stock reaction ≠ confirmed weakness in HBM demand

The KMI Expectations Framework

KMI evaluates earnings reactions using four layers.

1. Reported Results

Did the company beat formal expectations?

Here:

Yes.

2. Guidance

Was future guidance strong?

Here:

Yes, relative to published consensus.

3. Embedded Expectations

Had investors already priced in something even stronger?

Here:

Likely yes.

4. Valuation

How much future growth was already reflected in the share price?

After very large stock gains, the hurdle becomes much higher.

What Was Confirmed?

The evidence confirms:

  • Sandisk reported strong revenue and earnings
  • Western Digital reported strong revenue and earnings
  • both issued revenue guidance above formal LSEG consensus
  • both stocks fell sharply
  • both stocks had experienced exceptional prior rallies
  • Sandisk’s data-center revenue grew more than 400%

What Was Not Confirmed?

The selloff does not prove that:

  • AI demand collapsed
  • NAND demand collapsed
  • HBM demand weakened
  • SK hynix or Samsung earnings must fall
  • the memory cycle is over

Those require separate evidence.

What to Watch Next

Pricing

Does NAND and storage pricing keep rising?

Margins

Can current profitability levels be sustained?

Data-Center Demand

Does AI infrastructure spending continue?

Guidance Revisions

Do companies continue raising future forecasts?

Valuation

Does earnings growth catch up with the expectations already embedded in the stocks?

Key Takeaway

Sandisk and Western Digital did not fall because their results were bad.

They fell because:

good results were no longer enough

after extraordinary rallies.

The correct framework is:

Results vs. consensus vs. market-implied expectations

For Korean investors, this is especially relevant to AI-related semiconductor stocks.

Strong fundamentals can coexist with falling share prices when expectations have moved even faster than earnings.

Sources

  • Sandisk fiscal Q4 and FY2026 results
  • Western Digital fiscal Q4 and FY2026 results
  • Reuters, August 6, 2026

Korea Market Insight

Evidence Before Narrative

This article is for informational and educational purposes only and does not constitute investment advice.

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