Not financial advice. TheGatBull does not provide investment advice.
The short answer
For the week of September 7–11, the KOSPI finished +3.33%. But Monday alone was +4.61%, and the other four days combined came to −1.22%. The whole week’s gain sat in its first day.
That Monday, the US market was closed for Labor Day.
So over the same week, EWY (the iShares MSCI South Korea ETF) finished −0.08% — effectively flat. Not because the won weakened: the won actually strengthened 0.33%, which works in a US holder’s favor. The currency helped, and the scorecards still split.
That leaves one explanation. Seoul’s “this week” and New York’s “this week” were not the same week.
What this means for EWY holders
1. Your EWY is not broken. The “+3.3%” in Korean headlines and the “0.0%” in your account are measuring different windows — the KOSPI’s Monday surge is a move your ETF already paid for last Friday. 2. There is nothing to do. This is not tracking error and not a fee problem. Match the windows before you compare, and the two numbers stop disagreeing.
1. The week’s numbers (Sept 4 close → Sept 11 close)
All Korean figures are 3:30 PM KST KRX regular-session closes. No alternative-venue (NXT) aggregates.
| Instrument | Sept 4 | Sept 11 | Week | Currency |
|---|---|---|---|---|
| KOSPI | 6,687.21 | 6,909.91 | +3.33% | ₩ |
| KOSDAQ | 813.50 | 820.64 | +0.88% | ₩ |
| Samsung Electronics | ₩255,500 | ₩259,500 | +1.57% | ₩ |
| SK Hynix | ₩1,647,000 | ₩1,812,000 | +10.02% | ₩ |
| USD/KRW (Seoul 3:30 PM) | 1,350.4 | 1,345.9 | won +0.33% stronger | — |
US-listed instruments get their own table — their trading days are different.
| Instrument (US trading days) | Sept 4 | Sept 11 | Week | Currency |
|---|---|---|---|---|
| EWY (NYSE Arca) | $188.87 | $188.72 | −0.08% | $ |
| SKHY (Nasdaq, SK Hynix ADR) | $177.00 | $190.07 | +7.38% | $ |
⚠️ Do not subtract the returns in one table from the other. One set is in won, the other in dollars — the right way to compare them is in section 4.
2. One Monday made the week
| Day | KOSPI close | Change |
|---|---|---|
| Mon 9/7 | 6,995.39 | +4.61% (+308.18p) |
| Tue 9/8 | 6,954.52 | −0.58% |
| Wed 9/9 | 7,051.64 | +1.40% |
| Thu 9/10 | 7,033.92 | −0.25% |
| Fri 9/11 | 6,909.91 | −1.76% |
- Monday alone: +4.61%
- Tuesday through Friday combined: −1.22%
- Multiplied: 1.046084 × 0.987781 = 1.033301 → the weekly +3.33%. It ties out.
Inside the index, the same shape. Samsung Electronics made +5.68% on Monday and gave back −3.89% over the next four days. SK Hynix ran +8.26% on Monday and added another +1.63% after.
One thing we will not write: “the biggest one-day share of a weekly gain on record.” A superlative needs the past checked on the same basis, and we did not check it. What you have here is this week’s number.
For the record, the week’s intraday range: high 7,171.52 (Sept 8), low 6,802.50 (Sept 11) — a −5.15% span. Those are intraday prints, and they do not mix into the closing-basis numbers above.
3. The US was closed that day
Monday, September 7 was Labor Day. The NYSE and Nasdaq were shut — while Seoul traded normally. So the two markets ran different session counts this week:
| Sessions | Days | |
|---|---|---|
| Seoul | 5 | 9/7 · 9/8 · 9/9 · 9/10 · 9/11 |
| United States | 4 | 9/8 · 9/9 · 9/10 · 9/11 (9/7 closed) |
EWY and SKHY simply have no September 7 row in their daily data — the holiday proves itself.
And here is where the two ends of the week slip apart.
The start: on US Friday, September 4, EWY closed +4.60%. On Seoul Monday, September 7, the KOSPI closed +4.61%. How close those two numbers sit is plain to see — but they belong to different dates, and the US September 4 went into EWY’s last weekly statement. It is not in this week’s window.
★ We are not asserting here that “EWY front-ran Seoul.” We are placing the two numbers side by side with their dates attached. The day-level version of this mechanism has its own piece → What did EWY do on Labor Day?
The end: on US Friday, September 11, EWY closed +3.25%. But Seoul was already shut — its September 11 had ended at −1.76%. That +3.25% is information that now waits for Seoul’s next open, Monday September 14.
The start slipped, and the end slipped. Between them sits a 3.76-point gap — not a number you get from the two Fridays above, but from putting both scorecards in the same currency. That is section 4.
4. The currency is not the culprit
The usual suspect is “the won fell, so the dollar return got clipped.” This week ran the other way. USD/KRW went 1,350.4 (Sept 4) → 1,345.9 (Sept 11): the won strengthened 0.33%, which adds to a Korean asset’s dollar return.
Put both sides in dollars — the only way the comparison is valid:
| Item | Currency | Week |
|---|---|---|
| KOSPI | ₩ | +3.33% |
| Won | — | +0.33% stronger |
| KOSPI, converted to USD | $ | +3.68% |
| EWY, actual USD | $ | −0.08% |
| Gap | $ ↔ $ | 3.76 points |
The exchange rate was on the US holder’s side — and 3.76 points still went missing.
⚠️ “KOSPI in USD +3.68%” is a theoretical figure — no fees, no tracking difference, no cash drag, no tax. No real ETF prints it. It appears here only as the control that rules the currency out. And the gap is far too large for tracking error to explain — the windows are different.
5. Inside the index — the top two split
Roughly 40-odd percent of EWY sits in two stocks — Samsung Electronics and SK Hynix (iShares disclosure, as of Sept 4; weights move daily). The two split hard this week:
| Stock | Week (₩) |
|---|---|
| Samsung Electronics | +1.57% |
| SK Hynix | +10.02% |
| Spread | 8.45 points |
That subtraction is allowed — both are won returns. SK Hynix’s ADR, SKHY, made +7.38% in dollars. It differs from the Seoul shares’ +10.02% and neither is wrong: different currency, different trading days. Do not subtract the two into a “premium shrank by X” sentence.
Who bought and who sold this week — the by-investor flow data — we did not obtain. So it is not in this piece. Leaving it blank beats guessing a direction.
6. What it means for the Korean market
Set it against something a US reader already knows. If your 401(k) statement closes on Thursday, a 2% Friday rally is not on it. The statement is not wrong — the window is different. Nobody reads a Thursday statement and concludes their fund “can’t keep up with the market.”
The Korean market carries this structurally. Seoul starts its day before New York, prices everything while New York sleeps, and closes. Add one US holiday, and the mismatch hardens from a day into a whole weekly scorecard — which is exactly what happened: the one day that held the entire week’s gain fell on the day America was off.
This is the thing you cannot see about the Korean market without this week: Korea’s weekly result can concentrate into a single day, and when that day lands on a US holiday, a US holder’s “week” and Korea’s “week” stop being the same week. It happens several times a year, and it will happen again.
🎩 Under the Gat — Reading this as “EWY failed to track the KOSPI” gets it wrong. EWY does not buy Korean hours; it buys New York hours. Most of Seoul’s gain this week was priced on a Monday the US was closed — and that value was already printed on EWY’s last week’s statement. Before you compare scorecards, match the scorecards’ dates.
7. What to watch next week
- FOMC, September 15–16. The decision lands Wednesday afternoon US time; Seoul trades it first on Thursday morning — another place the windows slip. The week Korea said it would not mechanically follow the Fed was last week’s column.
- Chuseok closures ahead. Korea’s regular session closes Sept 24–25, plus the Sept 28 substitute holiday. That week, Seoul sits dark while the US trades — the mirror image of this week’s slip, already on the calendar.
- Seoul’s Monday, September 14. US Friday’s EWY +3.25% has not yet been priced in Seoul.
The takeaway
The KOSPI rose +3.33% this week, +4.61% of it on a Monday when the US was closed for Labor Day — so EWY finished at −0.08%. The won was strong, so the currency is not the story. The numbers do not disagree; the windows do. Next time a Korean weekly headline and your account disagree, check the calendar before you check the ETF. Curious what you actually own? Inside EWY · Last week’s scoreboard: the three days the KOSPI rose while every investor group sold.
FAQ
The KOSPI rose 3.3% — why is my EWY flat?
The two numbers measure different windows. Nearly all of the KOSPI’s weekly gain came on Monday, September 7, when the US market was closed for Labor Day — EWY’s “this week” only starts on September 8. The currency is not the cause: the won strengthened 0.33% this week.
Is this tracking error?
No. Tracking error measures how far an ETF drifts from its index over the same period, and it is usually far smaller. The 3.76-point gap here comes from the measurement windows being different.
Does that make EWY a worse product than the KOSPI?
Not on this week’s evidence. The slip changes direction week by week — this week it cut against the US holder; in weeks where the US moves first, it cuts the other way. Over longer horizons the effect washes out.
SK Hynix was +10.0% in Seoul but its ADR +7.4% — what’s the difference?
Different currency (won vs. dollar) and different trading days. Do not subtract the two into a single number; read each under its own label.
When is the Korean market closed next?
For Chuseok, the regular session closes September 24–25, and September 28 is a substitute holiday.
Sources
- Index and single-stock closes/OHLC: Yahoo Finance chart API, queried Sept 13 (^KS11, ^KQ11, 005930.KS, 000660.KS, EWY, SKHY). Korean rows tagged KRW · KSC/KOE · Asia/Seoul — vendor tags, not exchange-published attestations. All weekly and daily figures re-verified by multiplication checks.
- USD/KRW: Seoul FX market 3:30 PM weekly-session closes — Sept 4 = 1,350.4 (−8.90 won on the day) and Sept 11 = 1,345.9 (+6.70 won on the day), each re-confirmed on Sept 13 against multiple Korean outlets’ closing reports (three for Sept 4, four for Sept 11).
- Sept 7 Labor Day closure: NYSE/Nasdaq holiday schedules; EWY/SKHY daily data contain no Sept 7 row.
- Weekly KOSPI +3.33% and Monday’s +4.61% (6,995.39, +308.18p): cross-checked on Sept 13 against Korean market-wrap coverage; consistent with the Yahoo closes.
- EWY holdings weights: iShares disclosure, as of Sept 4.
- By-investor flow data for the week was not obtained and is not discussed.
Not financial advice. This article is for information only. TheGatBull and its author hold no position in the securities mentioned unless disclosed. Confidence labels are as of publication.