Bid price changes: the core idea
In foreign exchange (forex) quoting, the bid price is the price at which a market participant is willing to buy a currency pair (i.e., the market’s willingness to buy). During volatile markets, that willingness can change quickly. As a result, the displayed bid price may move, even if the “fair value” of the exchange rate is changing smoothly.
A useful way to think about it is: bid price is a live snapshot of supply-side willingness, not a single permanent number. When conditions shift, the snapshot can update in steps (jumps) rather than continuously.
Mechanisms that cause jumps in the bid
1) Order-book gaps (discrete liquidity)
Even when people describe markets as “continuous,” the actual willingness to trade is provided by orders at specific price levels. If there are few bids at the moment, the next available bid might be meaningfully higher or lower than the previous one. That creates a price gap: when the best available bid level changes, the displayed bid can “jump.”
2) Latency and quote delay
Volatility increases the rate at which prices and quotes change. If your quote feed, network path, or systems processing updates are slower than the rate of market change, you may observe a bid price that reflects information from a slightly earlier moment. This can make movements look abrupt, because updates arrive after underlying conditions have already changed.
Assumption for the example: suppose the underlying quote changes twice within 50 milliseconds, but your feed updates only every 100 milliseconds. You might observe only the second change, which looks like a sudden step.
3) Liquidity withdrawal and inventory effects
In volatile conditions, some participants reduce risk by withdrawing bids (and offers) or by making their quotes less aggressive. If fewer orders are willing to sit at the best bid, the market may step to the next available bid level, widening the gap and moving the bid.
This is not a “guaranteed” effect; it depends on participants’ risk limits, trading activity, and the specific flow of orders.
4) How orders are handled near changing quotes
When bid prices move, whether an order is executed depends on the order-handling rules in place. Common outcomes include:
- Full fill at an available price level.
- Partial fill if only some size exists at or near the referenced price.
- No fill (rejection or expiration) when the market moves away or required liquidity is not available.
Material limitation: if the bid changes between the time an order is placed and the time it is processed, execution may occur at a different level than the last displayed bid, or it may not execute.
Evidence or example using self-checking logic
You can verify the “jump” explanation without real-time data by checking the logic of discrete liquidity and timing:
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Discrete levels: Imagine two possible bid levels, 1.2345 and 1.2340, but only small size exists at 1.2345. When that size is taken or cancelled, the best bid becomes 1.2340, creating a visible step.
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Timing: If you record the timestamp of observed bid updates and compare them to your system’s processing cadence (how often you receive quotes), you can test whether observed steps align with delayed updates.
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Liquidity withdrawal: If bid size appears to drop while volatility rises (even without focusing on the exact numbers), it supports the liquidity-thinning idea: fewer resting bids means larger gaps between successive best bids.
Limitations and failure modes
- Correlation is not causation: Bid jumps can coincide with volatility, but the driver may be liquidity provision, update timing, or order-handling mechanics—not “volatility itself” as a single cause.
- Spreads and bid movement are related but not identical: Bid price changes can occur with the spread widening or narrowing; you need both bid and ask (or at least a clear definition of the quote you observed) to interpret meaningfully.
- Execution vs display: The bid you see may differ from the price relevant to your specific order because of latency and order-handling rules.
- Provider and venue differences: Quote behavior can vary across trading venues and market providers due to different matching, risk controls, and quote dissemination methods.