Direct answer
Rollover (often called swap) in forex is generally calculated from interest-rate related inputs for the two currencies in the trade, adjusted by the provider’s pricing conventions and applied per day. “Positive Correlation” is a relationship concept about how prices tend to move together across time; it does not, by itself, change the underlying interest-rate differential or the provider’s rollover rules.
Mechanism or definition
Positive correlation means that two variables tend to move in the same direction (when one rises, the other often rises too). In forex research, that usually refers to how currency pairs (or their returns) co-move.
Rollover is the carry cost or carry benefit of holding a position overnight. In simplified terms, it reflects the relative attractiveness of the two currencies’ interest rates, scaled by the position size and the trade’s direction (long vs short). Because real providers incorporate operational details, the final amount is not only “interest rate difference × size”; it also follows their daily timing, rounding, and sign conventions.
To explain the arithmetic without assuming any specific broker formula, use this generic model:
- Identify the two currencies in the pair.
- Use the provider’s interest-rate inputs for each currency (commonly derived from interbank or reference rates plus adjustments).
- Compute a differential representing how much carry the long leg earns relative to the short leg (or vice versa).
- Apply the position direction: holding a currency pair long is not the same as holding it short.
- Apply the provider’s rollover convention (including whether it is a normal single-day swap or a multi-day swap on certain dates).
Evidence or example
Assume you have a hypothetical provider that applies rollover as follows (this is an illustrative structure, not a guarantee of any real provider):
- There is a “base daily swap” for the long side and an equal-magnitude swap for the short side (with opposite sign).
- On a particular rollover day (often the one that spans a weekend gap), the provider charges or credits three times the daily amount instead of once. This is commonly called a triple-swap convention.
Example structure for directionality:
- If your trade is held overnight on a regular day, rollover uses one daily differential.
- If your trade is held overnight on the special day, rollover uses the same differential but multiplied by three.
- If you reverse direction (long vs short), the sign flips, turning a carry benefit into a carry cost (or vice versa), subject to the provider’s exact sign convention.
Where “positive correlation” fits: even if two pairs are positively correlated, the rollover computation still depends on the currencies you are actually holding and the provider’s swap rules for those currencies. Correlation does not change which currency leg is long/short, nor the provider’s interest-rate inputs.
Limitations and risks
- Provider conventions can dominate the outcome. Even with the same currency pair, different providers may apply different adjustments, rounding, or timing rules. That can make rollover amounts differ materially.
- Timing and rollover date alignment. A failure mode is assuming rollover is purely “calendar day based” without checking the provider’s rollover cut-off. If you hold through a different rollover window than expected, the number of days charged/credited may differ.
- Triple-swap surprises. On certain rollover days, the swap may be multiplied (commonly three). If you do not account for this, you can mis-estimate costs.
- Correlation does not imply carry similarity. Positive correlation describes price co-movement; it does not ensure similar interest-rate differentials, similar spreads, or similar swap behavior.
Verification or next question
To independently verify rollover facts for “positive correlation” research, treat it as two separate topics:
- Compute/confirm rollover mechanically: confirm the provider’s disclosed swap methodology, the reference interest inputs they use, the cut-off time, and whether they apply a triple-swap or similar multi-day convention on specific days.
- Confirm the correlation claim separately: use historical return calculations to estimate correlation, and remember that correlation is not stable and does not control swap arithmetic.
A useful next question is: “For the specific broker/provider and the exact trade direction, what is the disclosed formula or table for daily swap and any multi-day (triple) swap days, including the rollover cut-off time?”