Does the KOSDAQ Index Reflect Conditions Across All Small and Mid-Cap Stocks?
Understand the coverage of the KOSDAQ Composite and KOSDAQ 150, sector concentration, and how to interpret trading value, market breadth, and relative returns together.
The KOSDAQ index combines stock prices on the KOSDAQ market using market-capitalization weighting; it does not directly measure business conditions for all small and medium-sized companies. A few large constituents and sectors can drive the overall index. When interpreting the performance of KOSDAQ 150 products or individual growth stocks, first check how their composition differs from the Composite.
Company size and listing market are different classifications
Treating the KOSDAQ as simply a market for small companies misses an important part of index interpretation. The listing market is one classification, while market capitalization measures company size and changes with share prices and share counts. Because market capitalization influences the KOSDAQ Composite, larger companies within the market play a relatively greater role. The Korea Exchange provides the KOSDAQ 150 and industry and size indexes as well as the Composite. To assess whether a company's movement reflects a broad market factor or a sector factor, compare its return with these subindexes over the same period.
Compare market breadth with movements in trading value
When the Composite rises, check how widely gains are distributed across stocks. An increase in trading value is not conclusive evidence of buying conviction. Every executed trade involves both a purchase and a sale, so trading value shows only the scale of trading activity. It can also rise when large stocks plunge and shares change hands. Record broad index gains accompanied by a rising share of advancing stocks and participation across sectors separately from rallies in just a few companies. It is best to treat a one-day change separately from corporate earnings trends.
Align the starting points when comparing with the KOSPI
The KOSDAQ's lower numerical level than the KOSPI does not mean it is cheaper. Because the indexes use different bases, rebase both to 100 on the same starting date or compare their period returns. Relative strength does not automatically guarantee investment quality either. Their sector composition and exposure to financing conditions differ. To investigate a rise, examine improvements in earnings estimates, sector news, and index composition changes separately. When comparing a KOSDAQ 150 ETF with the Composite, check constituent coverage before considering costs.
Worked example
Hypothetical example: Rebase both the KOSDAQ and KOSPI to 100 on the comparison's starting date. If the KOSDAQ reaches 108 and the KOSPI 103 a month later, the difference in returns is 5 percentage points. Calculating the KOSDAQ's relative performance against the KOSPI as a ratio gives 108÷103-1=approximately 4.85%. The 5 percentage points and 4.85% serve different calculation purposes. Also check separately whether gains during this period were confined to a particular KOSDAQ sector.
What to check
- Distinguish between the KOSDAQ Composite and KOSDAQ 150 as underlying indexes.
- Check whether the proportion of advancing stocks aligns with the index's direction.
- Do not describe an increase in trading value as an increase in net buying.
- Compare performance against the KOSPI using returns over the same period.
Sources and primary materials
This is educational material about research methods. For an actual company decision, verify the filings and primary sources for the relevant period.