Taiwan's stock market has grown to about $5.3 trillion in market value, making it the world's fourth largest. On Sept. 23, Taiwan's benchmark TAIEX index rose 357.12 points, or 0.75%, to close at a record 48,157.29. According to MarketCapWatch data cited by Taiwanese media (as of Sept. 23), India ($4.94 trillion) and the UK ($4.86 trillion) now rank behind Taiwan.

So where does Korea rank? Seventh, at about $4.5 trillion, by the same MarketCapWatch data (as of Sept. 23). The interesting part is that just four months ago, Korea was ahead of Taiwan.

1. Korea is 7th, but four months ago it was ahead of Taiwan

In the same ranking, the top three are the US ($82.7 trillion), China ($21.22 trillion) and Japan ($8.59 trillion). After Taiwan in fourth come India and the UK in fifth and sixth, Korea in seventh and Canada ($4.45 trillion) in eighth.

In May, the order was reversed. As of May 11, the combined market value of Korea's KOSPI and KOSDAQ was about $4.66 trillion, putting Korea sixth in the world (Bloomberg data), ahead of Taiwan (about $4.33 trillion). Korea had passed the UK on April 27 and Canada on May 7 before overtaking Taiwan. But Taiwan took back the lead by late May (Bloomberg, June 1: Taiwan $5.15 trillion vs. Korea $5.04 trillion), and after the KOSPI crash on June 23 the gap widened, reaching about $800 billion on Sept. 23. Because the ranking is measured in dollars, exchange rates move it a little, but this reversal came far more from stock prices than from currencies.

2. In both markets, chipmakers make up about half

Taiwan's and Korea's stock markets look alike. TSMC alone accounts for nearly half of the Taiwan Stock Exchange's total market value. In Korea, Samsung Electronics and SK hynix made up 52.52% of the KOSPI's market value as of June 2.

So the size of both markets is effectively set by the share prices of a few leading chipmakers. On this year's results alone, both have soared: the TAIEX is up 66.27% so far this year, and the KOSPI has climbed about 68%, from 4,214.17 at the end of last year to 7,080.92 on Sept. 23.

3. The June crash widened the gap

The KOSPI closed at a record 9,114.55 on June 22. The very next day, it plunged 9.99%, or 910 points, in a single session, the largest point drop ever, and Samsung Electronics and SK hynix each fell 12%. Korean broadcaster MBC attributed the drop to worries about over-investment by US big tech firms and fears of a rate hike ahead of US inflation data. On Sept. 23, the KOSPI stood about 22% below its June record.

Meanwhile, Taiwan's market grew from about $4.33 trillion in May to about $5.3 trillion in September. As Korea slipped back and Taiwan moved forward, a narrow gap in late May grew to about $800 billion by September.

4. Both make chips, so why did they split?

The answer lies in what each country's champion sells. TSMC is a foundry: it manufactures chips designed by companies such as Nvidia. When AI chip orders grow, its sales grow with them. TSMC's August revenue was about NT$514.8 billion, up 53.3% from a year earlier, and its January-August revenue rose 39.3%.

Samsung Electronics and SK hynix mainly sell memory chips. Memory prices swing widely with supply and demand, so their shares are sensitive to one question: have prices peaked? When Korean chip stocks plunged in July despite strong earnings, KB Asset Management pointed to worries that memory prices were nearing a peak, a possible slowdown in AI spending by US big tech, and Chinese makers gaining share in DRAM.

5. What this ranking means for Korean investors

Ranking seventh in the world does not describe the size of Korea's economy. When the two memory makers that make up half of the KOSPI fell from their June highs, the KOSPI dropped about 22% and the ranking fell with it. It is less that Korean companies as a whole weakened and more that two memory stocks pulled the ranking down.

Taiwan is in the same position. With nearly half its market riding on TSMC alone, Taiwan's ranking would be shaken the same way if AI chip orders turned down. In both countries, the share price of one or two chipmakers effectively is the country's stock market ranking.

6. BITPRESS Insight

Taiwan at No. 4 and Korea at No. 7 is not a ranking of economies. It is closer to a ranking of what the chipmakers holding up each market sell. TSMC builds AI chips to order, so more orders mean more sales. Memory, by contrast, moves on whether prices have peaked, and the shares swing first.

That is why Korea's global stock market ranking is likely to keep rising and falling with expectations for memory prices. A headline about where Korea's stock market ranks in the world is less news about the Korean economy than news about two companies: Samsung Electronics and SK hynix.

Sources
https://www.taipeitimes.com/News/front/archives/2026/09/24/2003864800
https://focustaiwan.tw/business/202609230017
https://www.marketcapwatch.com/all-countries/marketcap/
https://www.seoul.co.kr/news/economy/securities/2026/05/12/20260512500031
https://www.digitaltoday.co.kr/en/view/54562/south-korea-stock-market-capitalisation-ranks-sixth-worldwide-overtakes-taiwan
https://globaltaiwan.org/2026/06/taiwans-stock-exchange-is-soaring/
https://v.daum.net/v/20260603180103486
https://www.dailian.co.kr/news/view/1658497/9000------2026
https://imnews.imbc.com/replay/2026/nwdesk/article/6832331_37004.html
https://www.mt.co.kr/stock/2026/09/23/2026092315351375598
https://m.news.nate.com/view/20251230n28296
https://pr.tsmc.com/english/news/3340
https://kbthink.com/investment/issues/korea-stock-market-outlook-2026-h2.html

Glossary
Market cap — A company's share price multiplied by its number of shares. Add up every listed company in a country and you get the size of that country's stock market.
TAIEX (Taiwan's benchmark index) — Taiwan's benchmark stock index, tracking all stocks listed on the Taiwan Stock Exchange; Taiwan's equivalent of Korea's KOSPI.
Foundry — The business of manufacturing chips that other companies design. TSMC is the world's largest.
Memory chips — Chips that store data (DRAM and NAND). Their prices rise and fall sharply with supply and demand.
KOSPI — Korea's main stock index, covering the main board of the Korea Exchange. Samsung Electronics and SK hynix are its two largest companies.