[Edaily Reporter kyoungeun kim ] As the stock market prepares to open in September, investors’ calculations are becoming more complicated. Looking at past statistics, September is considered a typical “bearish month” in the KOSPI market.

According to the Korea Exchange on the 31st, based on historical average percentage changes for the KOSPI and KOSDAQ, the average percentage change for the KOSPI in September was recorded at -0.59%. This is the second-lowest figure among the 12 months, following August (-1.43%). These figures represent the average monthly returns for the KOSPI from 1980 (when the composite index was first calculated) through 2025, and for the KOSDAQ from 1997 through 2025.
The downtrend was even more pronounced in the KOSDAQ market in September. During the same period, the KOSDAQ’s average monthly return for September was -3.21%, marking the worst performance among the 12 months.
In contrast, November was a month marked by a notable uptrend. The KOSPI rose an average of 2.48% in November, posting its highest annual gain, while the KOSDAQ also rose 2.28%, recording its second-highest gain after January (2.69%). In addition, the KOSPI maintained a relatively steady trend in July (2.18%), January (2.12%), and December (1.82%).
Stock market experts cite seasonal factors as the reason behind September’s weakness. Analysts note that this coincides with a period of concentrated portfolio rebalancing and profit-taking by institutional investors ahead of the end of the third quarter, as well as a cluster of monetary policy events by the U.S. Federal Reserve (Fed).
The question is whether this seasonal pattern will repeat itself this year. Two main viewpoints are at odds within the securities industry. One argues for caution given the rising uncertainty surrounding the U.S. Federal Reserve, while the other—the “valuation recovery” theory—suggests that the current KOSPI price reflects an excessive discount, leaving room for a rebound.
In fact, uncertainty surrounding the Fed’s interest rate policy is emerging as a key variable this September. In his first Jackson Hole speech last weekend, Fed Chairman Kevin Warsh left the door open for a rate hike, noting that there is no evidence of a meaningful improvement in core inflation.
Lee Kyung-soo, an analyst at Hana Securities, noted, “This poured cold water on expectations of strong earnings from NVIDIA and weighed on the market.”
Also on the horizon is the release of U.S. employment data this week, which is expected to be the biggest factor in determining the future direction of interest rates. Given that the July nonfarm payrolls report—which showed a shocking decline of 23,000 jobs—will be released on the 4th of next month, analysts explain that whether the labor market recovers in August will determine the validity of the data supporting the September–October rate hike scenario hinted at by Chair Wash at Jackson Hole. He noted, “Weakness in the labor market could actually have a positive effect on the market.”
Some analysts also point out that it is difficult to predict the stock market trend for September this year based solely on historical averages. They explain that the scale of share buybacks by SamsungElectronics(005930)and SK hynix(000660)remains a variable that could curb foreign selling, and that the excessive discount relative to earnings forecasts is a factor supporting the lower end of stock market valuations.
In a report released that day, Noh Dong-gil, an analyst at Shinhan Investment Securities, projected a September KOSPI range of 6,600 to 8,000 points. He stated, “Applying an interest-rate-adjusted fair price-to-earnings (P/E) ratio of 8.5 times to the 12-month forward earnings per share (EPS) of 1,205.9 points yields a price of 10,250 points, which fully reflects the consensus,” and “The closing price of 6,789 points on the 28th represents a price that acknowledges only 66.2% of the consensus,” he noted.
He explained, “Even at 8,000 points, there remains a 22% discount relative to the consensus,” adding, “Of the 33.8% discount currently reflected in the price, only about one-third has been recovered, while the remaining two-thirds are left as a buffer due to uncertainties surrounding next year’s earnings and the return on investment in artificial intelligence (AI).”
Share buybacks by SamsungElectronics and SK hynix are also key variables. Analyst Noh analyzed, “The two companies actually acquired 10.3 trillion won worth of their own shares between August 20 and 28, with 44.7 trillion won remaining under their planned buyback programs,” adding, “The market has not sufficiently factored in these companies as buyers capable of immediately filling the gap left by foreign investors.” In fact, the 8.05 trillion won acquired from August 24 to 28 is roughly equivalent to the 8.32 trillion won in net foreign selling on the KOSPI during the same period.
He predicted, “The volatility index (VKOSPI) has fallen from 97 at the end of June to 50 at the end of August, and the burden of single-stock leveraged trading and portfolio rebalancing has also decreased compared to the peak,” adding, “As volatility declines, there is potential for long-term foreign capital—which had reduced its risk exposure—to re-enter the domestic stock market.”
There are also forecasts that if the U.S. Federal Open Market Committee (FOMC) decides to keep the benchmark interest rate unchanged on the 17th of next month (local time), the market could actually gain upward momentum.
Lee Kyung-min, an analyst at DaishinSecurities, said, “Although the probability of a September rate hike has risen to the 60% range following the Jackson Hole meeting, it is highly likely that the August core Consumer Price Index (CPI) will hit a new annual low of around 2.4%, so the Fed will likely hold rates steady in September,” “September, which many investors view as a risk factor, could actually serve as a trigger to strengthen the upward momentum,” he noted.
DaishinSecurities analyzed that, in light of this, the upper end of the KOSPI’s trading range for September should be set at 8,500–9,300. The analyst noted, “The KOSPI’s forward P/E ratio stands at 5.63x, remaining near historic lows, which reflects skepticism regarding next year’s earnings,” and predicted, “If events in September help alleviate this skepticism, the index could rise to the 8,500–9,300 range, accompanied by a re-rating to a forward P/E of 7–8x.”