Net exposure per symbol is the wrong number for almost every question
A book flat on every line can carry a large directional position. Long EURUSD is long euro and short dollar, and the dollar leg of every pair on the board appears on no symbol screen anywhere.
Almost every risk screen in the industry shows net exposure per symbol. It is the correct number for deciding whether to hedge one symbol, and the wrong number for almost every other question. A book that is flat on every line can carry a large directional position, and a book that looks exposed on three lines can be carrying almost none.
Every FX position is two currency positions
A symbol is a convention, not a thing. Long EURUSD is long euro and short dollar in equal measure. The per symbol view treats each pair as an independent instrument, which means the dollar leg of every pair on the board is invisible even though it is the largest single exposure most brokers carry.
exposure(CCY) = Σ notional_base(CCY) − Σ notional_quote(CCY)Three positions. The per symbol net exposure is zero on two of them and small on the third, so the symbol screen shows a book with almost nothing on. The currency decomposition disagrees.
| Position | Symbol net | Base leg | Quote leg |
|---|---|---|---|
| Client long EURUSD 40M | +40M EURUSD | +40M EUR | −40M USD |
| Client long GBPUSD 25M | +25M GBPUSD | +25M GBP | −25M USD |
| Client short EURGBP 24M | −24M EURGBP | −24M EUR | +24M GBP |
| Net EUR | +16M EUR | ||
| Net GBP | +49M GBP | ||
| Net USD | −65M USD |
Illustrative figures, chosen to show the mechanism. Your own numbers will differ.
The dollar leg is the largest position on most retail books and the only one that is never displayed.
Correlation is exposure you have not named yet
Currency decomposition handles pairs that share a leg exactly. It does not handle instruments that move together without sharing one, and those are where the surprises come from. Gold against the dollar, an index CFD against its own constituents, two energy contracts at different delivery months, a currency pegged loosely to another.
- Index against constituents. A short index CFD and long positions in the same names are treated as unrelated by every per symbol view, and net out in reality.
- Managed and pegged currencies. Exposure to a pegged currency is exposure to the currency it is pegged to, until the peg moves, at which point it is something else entirely and much larger.
- Commodity and currency links. Books that carry gold and the dollar separately are carrying one position twice, with the sign depending on the regime.
- Regime dependence. The correlation that nets your book in a calm month is the correlation that goes to one in a stressed week, which is when every position stops offsetting and starts adding.
The practical consequence is that a correlation matrix estimated on a trailing window understates risk at exactly the moment risk matters. Using it to reduce a reported exposure figure is how a book ends up with a number that is reassuring and wrong.
Entities net legally, not economically
A group with several licensed entities holds risk in each one separately. Client money is segregated per entity, capital is held per entity, and a position in one cannot be used to cover a loss in another. The group view and the entity view are both real, and they answer different questions.
- 01Entity A long 40M EURwithin its own limit
- 02Entity B short 38M EURwithin its own limit
- 03Group net, 2M EUReconomically almost flat
- 04Hedged separatelyboth entities pay spread
- 05Capital held twiceagainst offsetting positions
Both errors are available in this structure and brokers make both. Hedging at group level a position that is concentrated in one entity leaves that entity exposed while the group report shows flat. Hedging at entity level positions that offset across the group pays spread twice for no reduction in economic risk. Deciding correctly requires seeing both views simultaneously, which requires the entity boundary to be an attribute of a position rather than a separate database.
What a usable exposure view contains
Four layers, always together
- Per symbol net, which is what you hedge with and the only layer most brokers have.
- Per currency leg, which is the true directional position and needs no estimation, only arithmetic.
- Per correlated group, with the correlation stated and dated, and a stressed variant alongside the calm one rather than instead of it.
- Per entity and per group, both shown, because the difference between them is a real cost that somebody is currently paying.
Recomputed on position change, not on a schedule
An exposure report produced at a fixed hour is a description of a book that no longer exists. The useful trigger is a threshold on the decomposed figure, evaluated whenever a position changes, which is a continuous computation rather than a report.
Limits set on the layer that carries the risk
Limits are usually written per symbol because that is the layer that is visible. If the real exposure is a currency leg, a set of per symbol limits can all be respected while the leg runs far past anything the risk committee would have approved. The limit has to sit on the same layer as the exposure it is meant to constrain.
Every input exists already: open positions with their symbol definitions, the entity each account belongs to, and a spot series to convert legs into one currency. They have to be held together, recomputed as positions move, and kept correct when a symbol is added or an entity is licensed. That is the work.