Market Structure and Liquidity for Retail Traders

Execution quality is decided by market structure — who is on the other side of your order and how deep the book is. Understanding this removes most of the mystery from unexpected fills.

The order book

An order book lists resting limit orders at each price level. Market orders consume that liquidity from the top down. When your order is larger than the resting size at the best price, the remainder fills at worse levels. That difference is slippage, and it is structural rather than unfair.

Market makers and internalisation

Some venues route retail flow to market makers who quote both sides continuously. Others internalise the order and act as counterparty. Neither arrangement is automatically bad, but the model determines where a conflict of interest could exist and should be disclosed publicly.

Session liquidity

• Overlapping major sessions generally produce the tightest spreads.
• Session opens carry high volume and high volatility simultaneously.
• Holidays and late sessions thin the book, widening spreads sharply.
• Scheduled news can evaporate depth for seconds at a time.

Gaps and why stops are not guarantees

A stop order becomes a market order when triggered. If price gaps past the trigger, the fill occurs at the next available level, which can be far worse. Guaranteed stops exist on some platforms at a premium. Knowing which type you hold is essential risk information.

Volatility regimes

Liquidity and volatility are inversely related in stressed conditions: exactly when you most want to exit, exiting is most expensive. Position sizing should assume the stressed regime, not the calm one.

Our LW Management review examines what execution and order-handling information is publicly available, and the risk framework explains how to size around it.