How to Track Dual-Listed Stock Spreads Over Time
A practical framework for turning one-off ADR or CDI price gaps into a cleaner historical spread view.
Quick Answer
To track a dual-listed spread over time, normalize both lines to the same economic unit, convert currency with the right timestamp, remove stale-market comparisons where needed, then chart the percentage premium or discount against its own history.
Why one-day comparisons are noisy
A single cross-listing spread can be misleading. It might reflect a stale quote, a currency move, a thin trading session, or a real change in demand.
The trend matters more than the snapshot.
Use one spread formula
Pick a reference line and keep it consistent:
Spread = (Adjusted secondary price - Reference price) / Reference price
The adjusted secondary price should already include the depositary ratio and FX conversion.
Watch the market-hour problem
If one market is closed, the spread is partly a timing artifact. You can still chart it, but label it carefully. For cleaner analysis, compare prices from overlapping sessions or use close-to-close windows that match the news cycle.
Compare against the stock's own history
A 2% discount might be normal for one pair and unusual for another. The better question is: where is today's spread relative to this pair's own range?
Look for:
- sudden moves after earnings
- persistent discounts after liquidity changes
- spread widening during market stress
- normalization after both markets trade
How StockResearch helps
StockResearch keeps the ratio and currency normalization in the workflow so the spread is easier to read over time.
Open the comparison tool and use the historical view to separate normal noise from unusual divergence.FAQ
Is a persistent spread an arbitrage?
Not automatically. Fees, taxes, liquidity, settlement, and conversion mechanics often explain why a spread persists.
Which market should be the reference?
Usually the market with deeper liquidity and stronger price discovery. That can be the legal home market, but it is not guaranteed.
Can FX alone move the spread?
Yes. A stale or mismatched FX timestamp can create a fake premium or discount.
This post is for informational purposes only and does not constitute financial advice.