Tech Stocks Lead NASDAQ; Costco Zscaler Bloodbath - May 29

The Big Picture

Tech stocks drove the Nasdaq's weekly outperformance even as individual names including Costco and Zscaler suffered sharp declines after reporting results. That split leaves investors weighing momentum in growth names against headline risk from earnings surprises and guidance revisions.

Today is May 29, 2026, and market action this week underscored how concentrated strength in a handful of tech names can lift indexes while company-specific shocks still inflict large losses for shareholders.

What's Happening

Markets this week showed divergent outcomes: sizable rallies among leading tech names, offset by dramatic post-earnings selloffs in select large-cap retailers and cybersecurity software. The numbers below capture the headline moves investors should digest and use in valuation work.

• Top weekly tech gains included a rise of 18.56%, highlighting outsized momentum in a subset of Nasdaq listings.
• Another notable tech advance measured 8.89%, underscoring that gains were not limited to a single outlier.
• The broader Nasdaq’s net change for the period registered 0.01%, indicating that concentrated winners offset wider weakness.
• The week’s activity took place in 2026, giving investors fresh data points for rolling forward valuation models and scenario analysis.

Costco and Zscaler were singled out for heavy declines after reporting results. The Seeking Alpha coverage described the moves as a "bloodbath" post-results, signaling sharp market reactions to earnings details or guidance updates. At the same time, strength among several tech names lifted the Nasdaq’s weekly leaderboard even as broader internals stayed mixed.

For valuation-focused investors this mix provides multiple data points. Rapid, large-percentage moves in individual names change multiples, alter relative valuations within sectors, and affect scenario probabilities you might use in discounted cash flow or comparable-company models.

Why It Matters For Your Portfolio

This bifurcated market matters because index-level performance can mask individual-stock risk. If you own concentrated tech exposure you may be benefiting from momentum. If you hold retailers or software names that reported earnings, your position could be hit hard immediately after results.

Who should care: growth investors tracking $NVDA or other AI/semiconductor leaders may see momentum continue but should monitor valuation expansion. Value and income investors with exposure to large-cap retailers like $COST could face short-term volatility following disappointing results. Traders will find amplified opportunities from these moves, while long-term allocators should reassess position sizes in light of volatility and updated fundamentals. Analyst commentary was not provided in the available source, so market reaction is the clearest gauge of near-term sentiment.

Risks To Consider

• Earnings Shock Risk, a company-specific miss or weak guidance can trigger outsized declines as seen with Costco and Zscaler.
• Concentration Risk, index gains driven by a handful of large tech winners can reverse quickly if momentum stalls, leaving broad-market returns weaker than headline indexes suggest.
• Valuation Reset, the steep percentage moves in individual names can push multiples to levels that require revisiting growth assumptions and margin trajectories.

What To Watch Next

Investors should track upcoming catalysts that could confirm whether tech strength is durable or transitory and whether earnings reactions continue to drive big stock-level dispersion.

• Upcoming earnings releases and management guidance from major tech and retail names, which can extend or reverse recent moves.
• Sector rotation metrics and breadth indicators, to see if gains are broadening beyond a few leaders.
• Key valuation metrics such as forward P/E, PEG ratios, and updated free cash flow projections after this week’s reports, using the multiple data points now available for analysis.

The Bottom Line

• Tech momentum lifted Nasdaq weekly leaders, but index strength hid sharp company-level declines in Costco and Zscaler after earnings.
• Use the new percentage moves, including 18.56% and 8.89%, to update scenario analyses and relative valuations.
• Expect continued volatility around earnings; treat recent post-results "bloodbath" moves as reminders of company-specific risk.
• If you hold concentrated positions, reassess sizing and downside scenarios rather than relying solely on index-level performance.
• Monitor upcoming quarterly reports and valuation metrics before making material portfolio changes.

FAQ

Q: How should I interpret the big percentage moves this week?

A: Large percentage moves like 18.56% and 8.89% reflect concentrated strength or weakness in individual names. Incorporate those moves into your valuation models and stress tests to see how they change portfolio outcomes.

Q: Does a Nasdaq gain mean my portfolio is safer?

A: Not necessarily. The Nasdaq’s modest net change of 0.01% this period shows index-level gains can mask significant dispersion. Check your holdings individually and review exposure to the specific stocks that drove the rally.

Q: What’s the immediate priority after a post-earnings "bloodbath"?

A: First, verify the earnings and guidance details that triggered the move. Then update downside scenarios, reassess position sizing, and decide if you need to rebalance based on your risk tolerance and long-term plan.