The Nikkei 225, BSE Sensex and Shanghai Composite are not interchangeable measures of “Asia.” They cover different markets and use different construction rules. A useful comparison needs matching dates, return types and currencies—not just three headline index levels.
What each index actually measures
| Index | Coverage | Weighting approach |
|---|---|---|
| Nikkei 225 | 225 selected domestic stocks from Tokyo Stock Exchange’s Prime Market | Price-weighted, with methodology adjustments |
| BSE Sensex | 30 selected BSE-listed companies | Free-float market capitalisation |
| Shanghai Composite | Eligible Shanghai-listed securities, including A and B shares | Total market capitalisation under the index rules |
Nikkei’s official factsheet describes a selected 225-stock, price-weighted benchmark. It is not a list of Japan’s 225 largest companies by market value. BSE’s Sensex index comparison identifies the standard Sensex as free-float market-cap weighted; its equal-weight version is a different index.
The Shanghai Stock Exchange overview explains the Composite’s broad Shanghai coverage and total-capitalisation basis. Its 2020 methodology amendment introduced eligibility changes including risk-warning exclusions and listing-age rules. Therefore, “every Shanghai stock without exception” is an inaccurate shortcut.
Why weighting changes the story
A stock’s influence depends on the index rules, not how familiar its brand is. In a price-weighted framework, adjusted share prices matter; in a capitalisation-weighted framework, company size and any applicable float adjustments matter. Check the current provider documents before attributing a day’s index move to a particular company.
Hypothetical contribution example: a constituent with a 10% starting weight that rises 5% contributes approximately 0.5 percentage points to a simple weighted return, with other holdings unchanged. A stock with a 1% weight making the same move contributes about 0.05 percentage points. This is a simplified illustration, not an attribution for any index above.
Compare percentages, sessions and return variants
- Use the same interval. One market’s closing return and another’s still-changing intraday return are not equivalent observations.
- Record the trading date. A holiday may leave one screen showing an earlier session, even when both pages were opened today.
- Specify the time zone. The date a headline appears in your country may differ from the underlying exchange’s session date.
- Match the return type. Price changes exclude the reinvestment treatment captured by a total-return series. Do not mix the two.
- Check the exact instrument. An index, a futures contract, an ETF and a broker’s derivative can have different prices and trading arrangements.
Local-market gains are not your home-currency return
Hypothetical example: suppose an unhedged holding gains 10% in its local currency, while that currency loses 8% against yours. The translated return is (1.10 × 0.92) − 1 = 1.2%, before costs and taxes—not 10% and not exactly 2%. The relevant exchange-rate change is the local currency’s value in your home currency.
A currency-hedged fund has different mechanics and costs. The currency printed beside an ETF’s trading price does not by itself establish whether the underlying exposure is hedged. Read the product documents.
A reusable Asian-market research note
Before sharing a market summary, fill in these fields: index name; source URL; session date; observation time and zone; percentage change; price or total return; currency; and explanation labelled as interpretation. Leave a field blank rather than inventing a missing value.
Then write one sentence on what the evidence does not show. For example: “This index move does not establish that all companies in the country rose.” That distinction keeps a concise market post useful without overstating its meaning.
Use the economic calendar for scheduled-event context. For another example of why index labels matter, read our Nasdaq and Dow comparison.
Common questions
Does Shanghai Composite represent every Chinese equity market?
No. It is a Shanghai benchmark, not a combined measure of all mainland and Hong Kong listings.
Does the fastest-growing economy guarantee the best stock return?
No. Economic growth alone does not tell you the purchase valuation, shareholder dilution, index exposure, currency outcome or investment costs.
Correction note: the earlier “today’s updates” and country-return predictions have been removed; the Nikkei selection description has been corrected. Cover: AI-generated conceptual illustration, not an actual cityscape or market dataset. Corrections policy.