July 19 Stock Market Report: AI Chip Sector Weakness, Micron, AMD, and Alphabet Lead Big Tech Lower

Sector-Wide Semiconductor Weakness and Big Tech Earnings Defense

According to global stock market data from July 17, 2026, major large-cap technology stocks, led by Artificial Intelligence (AI) semiconductor firms, experienced a broad sell-off. Micron fell 0.06% from the previous day's 904.28 won to close at 853.20 won, with a market capitalization recorded at approximately 0.96 trillion won. During the same period, AMD also closed down 0.05% from the previous day at 500.94 won. This weakness in semiconductor stocks is not merely a short-term fluctuation but is acting as a factor increasing volatility across the broader market.

As shown in the table, Broadcom and Alphabet also recorded declines of 0.05% and 0.04%, respectively, stabilizing in a downward trend. However, the fundamental gap between these stocks is stark. AMD has a Price-to-Earnings Ratio (PER) of 166.4, but its Earnings Per Share (EPS) growth rate reaches 16,435.6%, clearly reflecting the market's high expectations for growth. In contrast, Micron appears relatively undervalued with a PER of 19.3. This disparity suggests that within the capital-intensive AI infrastructure market, the speed of profit recovery and market share vary significantly by company.

Contraction in Investor Sentiment and Sector Valuation Conflicts

The market's instability is intertwined with structural issues in the capital markets. Seoul Mayor Oh Se-hoon recently criticized the overheating of single-stock leverage derivatives, pointing to them as a cause of market volatility. The circuit breaker (sidecar) has already been triggered 37 times in the KOSPI market this year, significantly exceeding the annual record of 26 during the 2008 global financial crisis. Rather than normal supply and demand, the rapid inflow and outflow of speculative funds targeting specific sectors are exacerbating sharp stock price swings. The consecutive decline in U.S. semiconductor stocks over the holiday is expected to act as a direct headwind for the domestic market.

NVIDIA, dominating the market with a capitalization of 5.02 trillion won, underwent a slight correction of 0.02%. However, given its PER of 31.8 and EPS growth rate of 6,599.3%, the price decline is difficult to attribute to fundamental deterioration. The problem lies with Tesla and Meta. Tesla’s PER has soared to 358.8, while its EPS growth rate has plummeted to -4,709.0%, creating extreme pressure regarding past golden crosses. Meta also saw its EPS growth rate turn negative at -256.0%, reflecting concerns over earnings slowdown. Whether Big Tech firms can stage an earnings turnaround has emerged as the key variable determining market direction.

Full-Scale Earnings Season and Market Outlook

As U.S. Big Tech firms approach their Q2 earnings announcements, investors are adopting a conservative stance. For Alphabet in particular, cloud revenue growth and massive AI capital expenditure plans are serving as key evaluation metrics. Alphabet currently records a PER of 28.3 and an EPS growth rate of 3,419.4%, suggesting a high likelihood of continued appreciation in corporate value. However, macroeconomically, the semiconductor tariffs under review by the White House pose a short-term risk to the market. If tariffs are imposed, margin deterioration for manufacturing and design firms like Micron and AMD seems inevitable.

Entering the full-scale earnings season next week, the stock market is expected to form a highly polarized trend depending on corporate guidance. As AI models like ChatGPT become widely used as investment assistants, algorithm-based mechanical trading is expected to continue amplifying trading volume volatility. While securities firms expect record-breaking earnings due to the surge in domestic trading volumes, the risk associated with leverage investment in individual stocks has reached its peak. In conclusion, the market is at a point where investors should restructure portfolios toward high-quality stocks with low PERs and clear profit growth, maintaining a defensive investment bias. Following earnings announcements, stocks that meet market expectations are likely to see a rebound in buying interest, demonstrating resilience.