Spread Widening

What Spread Widening means

Spread widening happens when liquidity providers pull back. Faced with uncertainty about where the true price is, or with the risk of being picked off by faster participants, they quote less size at worse prices, and the aggregated best bid and offer move apart. The pattern is highly predictable in its timing even though its magnitude is not: the seconds around scheduled economic releases, the daily rollover at 5pm New York, the Sunday reopen, thin holiday sessions and unscheduled political or central bank surprises.

The direct cost is obvious, but the indirect effects are usually larger. Stop losses and take profits are triggered by the relevant side of the quote, so a widening episode can trigger a stop on a long position when only the bid, not the mid-price, reached the level, producing an exit the chart appears not to justify. Widening also inflates the margin requirement's effect on floating equity, which in an already stressed account can accelerate a margin call or stop out.

Mitigation is largely a matter of timing and order placement. Avoiding market orders in the moments around known events, placing stops beyond the range that a typical widening episode reaches rather than at obvious round numbers, and reducing size during thin sessions all help. Some brokers publish historical spread data by hour, which is a more useful comparison than an advertised average.