It was a week when the Korean stock market made new history. The Korea Composite Stock Price Index (KOSPI) started at 3,407.78 on Sept. 15 and climbed intraday to 3,467.89 on the 19th, setting an all-time high. It then pulled back on profit-taking and closed at 3,445.24. The KOSDAQ also rose from 849.64 to 863.11 over the same period. It was the first time since last July that the KOSDAQ broke above the 860 level.
The "semiconductor rally" lifted the stock indexes. Both Samsung Electronics and SK hynix, No. 1 and No. 2 by market capitalization on the KOSPI, hit their highest prices of the year. Shares of semiconductor materials, components, and equipment corporations also jumped.
This week (Sept. 22–26), market sentiment will hinge on whether the semiconductor rally can continue.
U.S. Micron Technology (MU; Micron) could be a turning point with its fiscal year fourth-quarter (June–August) results. Micron will release its earnings and its outlook for fiscal year 2026 (September 2025–August 2026) early on the 24th Korea time. Micron is the first in the memory chip industry to report quarterly results and is called the "barometer of the semiconductor cycle."
The market expects Micron to have posted fourth-quarter earnings per share (EPS) of $2.77. Earlier, Micron also raised its fourth-quarter EPS guidance to $2.85.
U.S. inflation data also bears close watching. With the U.S. Central Bank, the Federal Reserve (Fed), having cut the benchmark rate by 0.25 percentage points and hinting at two additional cuts by year-end, a spike in inflation could trigger a pullback in a rising market.
The personal consumption expenditures (PCE) price index for August, a key inflation gauge the Fed monitors when setting currency policy, is due late on the 26th Korea time. The market expects a 2.7% gain from a year earlier and a 0.3% rise from the previous month.
As the week moves into the latter half, investors should also consider the possibility of profit-taking ahead of a long holiday. The KOSPI's valuation has topped 11 times on a 12-month forward price-earnings ratio (PER; market capitalization ÷ net income) basis, and the 12-month trailing price-to-book ratio (PBR; market capitalization ÷ net worth) is above 1.1 times, adding to the burden.
With Rosh HaShanah, the Jewish New Year, running from the 22nd to the 24th and book closing possibly underway, foreign investor flows may shrink. Yu Myung-gan, a researcher at Mirae Asset Securities, said, "Foreign equity ownership in the KOSPI is in the 33% range, lower than 35% last July, and cumulative net buying suggests there is still room for inflows," but noted, "It is necessary to be mindful of the possibility of a correction due to downward revisions to third-quarter (July–September) and fourth-quarter (October–December) corporations' earnings."
Sector-by-sector divergence is likely to continue. For example, hotels, casinos, and cosmetics have emerged as beneficiaries as China allows visa-free entry for tourists and ahead of the Asia-Pacific Economic Cooperation (APEC) summit. In particular, expectations are likely to grow as U.S. President Donald Trump and China's President Xi Jinping are scheduled to visit Korea and meet.
Na Jeong-hwan, a researcher at NH Investment & Securities, projected that growth stocks such as healthcare or software, whose share prices have risen relatively less, could draw attention. He especially assessed that AI software also has policy momentum, making it highly attractive.