August 18 Review: KOSPI Fell 1.55%, Alongside US Equity Declines

Correction — 22 October 2026: The original 0.83% Korean gain is corrected to a 1.55% decline. The daily observation is dated August 18, rather than the publication date of August 19. Claims of Korean decoupling and rotation into its equity market are withdrawn. This is a retrospective review using daily history retrieved on 2026-10-22, not a live report or a reconstruction of every quote available at original publication.

Reconstructing the Korean return

The Korean index moved from 6,977.94 on 2026-08-14 to 6,869.83 on 2026-08-18. Dividing the later value by the earlier value, subtracting one and multiplying by 100 gives -1.55%. The previous article reported +0.83%. The difference is material because it reverses the direction of the return.

Dated observations and calculations

Check whether the alleged divergence exists

KOSPI fell from 6,977.94 on August 14 to 6,869.83 on August 18, the next available Korean observation in the provider series. The S&P 500 fell 0.69% and the Nasdaq fell 1.33% in their own daily comparisons. All three changes were negative. The Korean comparison also spans a longer calendar gap, so matching the signs does not make the observation windows identical.

Method and limits

Percentage changes use (value ÷ previous available daily value − 1) × 100, before rounding. Yield changes use the difference in percentage-point quotes multiplied by 100 to obtain basis points. Currency values are local-currency units per US dollar. Index levels are in points; futures quotes are in US dollars per barrel for WTI and per troy ounce for gold.

Each linked Yahoo Finance history is the data source for that row. These provider observations have not been independently checked against exchange settlement records. The futures series can change its referenced contract over time and should not be treated as the return on a continuously held investment. A date shared by two markets does not make their closing times simultaneous.

The earlier news-based explanations are omitted because their relevance to these measured moves was not established. For the calculation workflow and trading-session examples, see How to Read Daily Market Returns Without Mixing Trading Sessions.

Written by

James Yoo

James Yoo is the editor of Global Invest Daily. He follows global macro and cross-asset markets daily — Federal Reserve and ECB policy, Middle East energy dynamics, China and emerging markets — and writes scenario-based analysis of how geopolitical events transmit into equities, bonds, FX, and commodities. Every post follows the site's editorial standards: in-line attribution for every external statistic, no directive investment advice, and published corrections. Reach him via the site's Contact page.