Aggregators and Fading: Why the Best Bid Can Vanish
Posted: Mon Oct 26, 2026 11:55 am
A liquidity aggregator collects streams from multiple providers and presents a single consolidated price, built from the best bid and best offer across all sources. In theory, this narrows the spread below what any one provider offers alone.
The picture is more subtle in practice. Providers adjust quotes when they sense that an aggregator routes aggressive flow, and a visible best price may disappear before the order arrives. This is sometimes called fading. Aggregators try to manage it by ranking providers on fill rates and rejection rates, then routing accordingly.
Netting adds complexity. Some aggregators offset client orders internally before sending any residual to providers, which changes both the spread and the number of external fills. Others apply skew to quotes in response to broker inventory, making one side slightly cheaper to encourage offsetting trades.
For scalpers, a broker using aggregation may display tight, variable spreads that widen during stress as providers pull quotes. A narrow spread in calm hours is therefore only part of the story. Behaviour during volatility is far more telling.
The picture is more subtle in practice. Providers adjust quotes when they sense that an aggregator routes aggressive flow, and a visible best price may disappear before the order arrives. This is sometimes called fading. Aggregators try to manage it by ranking providers on fill rates and rejection rates, then routing accordingly.
Netting adds complexity. Some aggregators offset client orders internally before sending any residual to providers, which changes both the spread and the number of external fills. Others apply skew to quotes in response to broker inventory, making one side slightly cheaper to encourage offsetting trades.
For scalpers, a broker using aggregation may display tight, variable spreads that widen during stress as providers pull quotes. A narrow spread in calm hours is therefore only part of the story. Behaviour during volatility is far more telling.