Direct answer
Raw Spread is the price difference you see as the market’s “bid–ask” for a raw feed, typically before additional markups or simplified adjustments. During volatile markets, it can change quickly because the order book gets thinner, quotes move faster than systems can respond, and the matching engine may need to execute using the nearest available liquidity rather than the original displayed price.
Mechanics: what changes and why
To understand why Raw Spread can widen, separate stable mechanics from variable market conditions:
- Order-book depth and gaps. Raw Spread depends on the number of buy and sell orders near a given price. In calm periods there are often multiple levels of liquidity close together. In volatile periods, participants may not place or maintain orders at the same prices, so the next available quote is farther away. That increases the visible bid–ask distance.
- Liquidity withdrawal. When conditions worsen (for example, rapid price moves or uncertainty), some market participants may reduce how much liquidity they provide. That can remove quotes at specific levels, leaving a wider “gap” until new orders appear.
- Latency and update mismatch. Even if the displayed raw spread exists at one instant, market prices and the order book can update between the moment a quote is shown and the moment an order is processed. If the executed side uses quotes after an update, the effective raw spread around the execution can differ from the previously displayed value.
- Order handling and execution logic. Execution systems may route, queue, partially fill, or match against the best currently available prices. If the exact price level you expected is no longer present by the time execution occurs, the fill may occur at a worse level, making the observed spread effectively wider.
Evidence or example you can reason through (with assumptions)
Consider a simplified order book snapshot at time T0:
- Best bid: 1.10000
- Best ask: 1.10005 So the displayed Raw Spread is 0.00005.
Now assume the market moves quickly and you place an order at T1, but execution uses liquidity that is present at T2.
Two common paths to a wider effective spread:
- Gap formation: If orders between 1.10000 and 1.10005 are withdrawn, the next best ask might jump to 1.10010 by T2. The effective spread becomes 0.00010.
- Quote lag: If your system receives an updated order book slightly late, it may act on a wider gap that formed between T1 and T2. Your execution uses the “best available at execution,” not the “best you saw earlier.”
Material limitation: this example assumes a single discrete jump for clarity. In real markets, changes can be continuous and your results depend on the exact timing between quote display, order submission, routing, and matching.
Limitations and risks (what can fail in your understanding)
- Displayed vs executed difference. A key failure mode is assuming the displayed raw spread equals what you effectively trade. Volatility, latency, and matching rules can break that link.
- Variable external conditions. Order-book behavior depends on trading activity, risk appetite, and overall liquidity. Historical patterns do not guarantee future behavior.
- Provider or venue-specific handling. Even with the same underlying market, different execution handling (queueing, partial fills, routing) can change observed results.
- Data limitations. If you only observe quotes at one time or only use displayed metrics, you may miss the timing of the order execution.
Verification: how to independently check the claim
To verify how Raw Spread behaves during volatility (without relying on predictions), use a method that compares quote timing and execution timing:
- Record both displayed quotes and execution outcomes for the same instrument and time window, under clear assumptions about what you measure as “raw.”
- Segment by market regime (relative calm vs fast movement) using observable movement intensity rather than predictions.
- Check timing consistency: evaluate whether larger differences appear when delays or fast updates are more likely.
- Look for liquidity gap signatures: if effective spreads widen even when displayed spreads look similar for a moment, it often indicates gaps and update mismatch.