What is a spread, and why it matters
A spread is the difference between the quoted buy price (ask) and sell price (bid). In liquid markets, many participants compete to trade, so bid and ask prices are updated frequently and stay relatively close. In low liquidity pairs, fewer quotes and fewer standing orders can cause the bid and ask to drift farther apart.
When a spread is wider, the immediate cost of entering or exiting a position is higher, because you typically pay the ask to buy and receive the bid to sell.
What affects the spread in low liquidity pairs
1) Liquidity depth and order-book “distance”
Low liquidity pairs often have thinner order books. That means there is less available size near the current price. If a trade consumes the available bids or asks, the next best quotes may be at a noticeably different price level. This increases the observed spread and can also increase price jumps between consecutive quotes.
Assumption for this explanation: the market is not continuously supported by a large number of standing bids and asks at many price levels.
2) Volatility and quote-update speed
Volatility is how much prices move over time. In faster-moving conditions, quotes can become stale quickly. Market makers or liquidity providers may widen spreads to reduce the risk of being bought out or sold too far from their reference price before they can adjust.
A simple mental model: if price moves significantly between quote updates, the “fair” bid/ask range must expand to remain accurate for incoming orders.
3) Execution venue and matching mechanics
Spreads reflect how and where orders are matched and how quotes propagate through the system. Different venues (or different routing paths) can change:
- how quickly new bids and asks appear after a price move,
- how much competition exists for price priority,
- whether orders are matched internally, externally, or across different pools.
Even with the same underlying market conditions, execution mechanics can lead to different realized costs.
4) Transaction costs, compensation, and effective spread
What you pay is not only the visible bid-ask difference. Costs may include commissions, financing-related charges, and fees tied to execution type or account settings. Together, these can change your effective spread (the total cost of entering and exiting relative to the mid-price).
Assumption for separation: the quoted spread can be different from the total cost once commissions and other charges are included.
5) Provider and policy effects during stress
Providers may apply controls when liquidity is poor or market moves quickly. Examples include:
- reduced quote availability,
- wider internal pricing ranges,
- partial fills with later completion,
- changes to how orders are handled when depth is insufficient.
A key limitation: these behaviors can be intermittent and depend on current conditions, so the same pair may show different spread characteristics at different times.
Evidence or example you can reason through (without live prices)
Consider a low liquidity pair with a quoted bid at 1.0000 and ask at 1.0005, giving a spread of 0.0005 (in price units). Now imagine that only a small amount is available at those levels. If a buy market order arrives that consumes the available ask liquidity, the next ask may be much higher, so the new ask could jump, and the next bid may also adjust. In that scenario, the spread widens because the market must “reach” further to find executable prices.
This thought experiment shows a cause-and-effect chain:
- thin depth → orders consume available quotes → prices jump to the next available levels → spread widens.
Limitations and failure modes to watch for
- Past behavior may not predict future spreads. Liquidity can appear suddenly (or disappear) due to broader market conditions.
- Quotes may not equal realized prices. Fast markets, partial fills, and changing depth can make the realized cost differ from the displayed spread.
- Volatility and liquidity interact. Wider spreads can be both a cause of slower trading and a response to rapid price movement.
- Provider behavior can dominate outcomes. In low liquidity, execution rules and internal handling can outweigh “headline” spread expectations.