KOSPI closes at 6,820.02 on August 31, 2026 — down 175 points at the open, saved by buybacks
The KOSPI closed at 6,820.02 on August 31, 2026, up 31.14 points or 0.46 percent, but the close conceals the day. The index opened down 175.30 points at 6,613.58, a 2.58 percent fall, because news of a US-Iran exchange of fire near the Strait of Hormuz arrived before the Seoul open. It then reversed during the session. Two domestic forces did the work. Samsung Electronics filed to buy 2 million of its own shares and SK hynix 650,000 shares on the open market, instalments of buyback programmes running to 15 trillion won by November 21 and 40 trillion won by November 19. Separately, MSCI struck its August Korea index rebalancing at that day's close, with the revised index effective September 1, concentrating passive-fund trading into the closing auction. Samsung Electronics rose 1.17 percent to 260,000 won and SK hynix 1.27 percent to 1,674,000 won, while the KOSDAQ fell 0.49 percent to 834.29
The three lines
- Close — KOSPI 6,820.02, up 31.14 points (0.46%). It had opened down 2.58 percent
- Reversal — buyback filings from Samsung Electronics (2m shares) and SK hynix (650k shares) absorbed selling
- Overlay — MSCI's Korea rebalancing was struck at the same close, effective September 1
Key questions
- What was the KOSPI close on August 31, 2026?
- **6,820.02, up 31.14 points or 0.46 percent.** Reading only that number misreads the day. The KOSPI **opened at 6,613.58, down 175.30 points or 2.58 percent**, because news of a direct US-Iran exchange of fire near the Strait of Hormuz landed before the Seoul open. From that opening level to the close, the index recovered roughly **206 points**. The companion figures: the KOSDAQ fell 4.12 points, or 0.49 percent, to **834.29**, and the won closed at **1,368.6** per dollar. A rising KOSPI alongside a falling KOSDAQ tells you the gain came from **a handful of large caps**, not from the market as a whole.
- How does a buyback support the index?
- **Because real buy orders enter the market.** On August 31 Samsung Electronics filed to purchase **2 million** of its own shares on the open market — about 514 billion won at that day's close — and SK hynix **650,000** shares, roughly 1.09 trillion won on the same basis. These are not one-off announcements but single days of large running programmes: Samsung Electronics is buying **15 trillion won** of stock from August 24 through November 21, and SK hynix **40 trillion won** from August 20 through November 19, with a combined remainder reported in the mid-40-trillion-won range. The flow shows up in the statistics — **net buying by the 'other corporations' category exceeded 8.5 trillion won over six sessions**, which is where company buybacks are classified. But the two programmes differ in purpose: Samsung Electronics is buying for **employee share compensation**, which returns to the market later, while SK hynix is buying **to cancel the shares entirely**, which permanently reduces the share count.
- What did the MSCI rebalancing do?
- **It concentrated passive trading into the August 31 closing auction.** MSCI applies its August review at the **August 31 closing price**, with the revised index effective **September 1**. In the Korea index, **LG Innotek was added** and **HLB, LG Display, POSCO International and Samsung Epis Holdings were removed**. ETFs and index funds tracking the index must trade at the same closing price the index uses, or they accumulate tracking error — so unusually large volume clusters in the final minutes of a rebalancing day. Korean media called August 31 a **closing-price standoff**: index-driven selling from the removed names met buyback demand in the same window. The mechanics of index rebalancing are covered separately in "What MSCI rebalancing is."
KOSPI 6,820.02, up 31.14 points (+0.46 percent). The last trading day of August.
That close does not describe the day. The index opened down 2.58 percent.
1. The path
| Point | Index | Change |
|---|---|---|
| Open | 6,613.58 | −175.30 pts (−2.58%) |
| Close | 6,820.02 | +31.14 pts (+0.46%) |
| Recovery from the open | — | about +206 points |
The weak open came from abroad. Before the Seoul session, the United States and Iran exchanged direct fire near the Strait of Hormuz ("US and Iran exchange fire on August 31, 2026").
Other readings from the same session:
| Indicator | August 31 |
|---|---|
| KOSDAQ | 834.29 (−4.12 pts, −0.49%) |
| Won per dollar | 1,368.6 |
| Samsung Electronics | 260,000 won (+3,000, +1.17%) |
| SK hynix | 1,674,000 won (+21,000, +1.27%) |
The KOSPI rose while the KOSDAQ fell. That combination signals a gain concentrated in specific large caps — and the two large caps in question were Samsung Electronics and SK hynix.
2. What did the lifting — buybacks
Both companies filed open-market purchases on August 31.
| Company | Filed volume | Value at that close | Programme |
|---|---|---|---|
| Samsung Electronics | 2,000,000 shares | ~514bn won | Aug 24–Nov 21, 15tn won |
| SK hynix | 650,000 shares | ~1.09tn won | Aug 20–Nov 19, 40tn won |
The mechanism is not subtle: real buy orders arrive. When foreign investors sell, someone is on the other side.
The flow is visible in the statistics. Net buying by the "other corporations" category exceeded 8.5 trillion won over six sessions — the category into which a company buying its own stock falls.
But the two programmes are not the same thing.
| Company | Purpose | What remains in a year |
|---|---|---|
| Samsung Electronics | Employee share compensation | Shares return to the market later |
| SK hynix | Full cancellation | Share count falls permanently |
The difference between cancellation and compensation is covered in "What a share cancellation is." The same phrase — buying back stock — leaves different things behind.
3. The overlay — MSCI's August review
A second force was pinned to the same closing price.
MSCI applies its August review at the August 31 close, with the revised index effective September 1. For Korea:
| Action | Names |
|---|---|
| Added | LG Innotek |
| Removed | HLB · LG Display · POSCO International · Samsung Epis Holdings |
ETFs and index funds tracking the index have to trade at that same closing price or they book tracking error. So the last minutes of a rebalancing day carry far more volume than usual.
Index-driven selling from the removed names met buyback demand in that window, which is why Korean media described August 31 as a closing-price standoff. The mechanics are covered in "What MSCI rebalancing is."
4. What is still unresolved
- Session low — Whether 6,613.58 was also the day's low was not confirmed.
- Investor flows — Foreign, institutional and retail net figures for August 31 were not confirmed.
- Execution — Whether the filed buyback volumes were fully executed that day is not disclosed. A filing is an intent to buy.
- Passive flows — Estimated fund flows from the MSCI change are brokerage estimates, not final tallies.
- Cumulative buybacks — Programme execution through August 31 varied across reports and was not fixed here.
Sources
- Money Today — KOSPI closes at 6820.02, held up by Samsung and SK hynix buybacks
- Asiae — KOSPI closes up 31.14 points at 6820.02 (+0.46%)
- Asiae — KOSPI opens down 175.30 points at 6613.58 (−2.58%)
- Businesskorea — KOSPI reverses to close above 6,800; won ends at 1,368.6
- EBN — MSCI rebalancing versus buybacks: a closing-price standoff in Samsung and SK hynix