How Order Book Depth at 5, 10, and 50 Bps Affects Slippage

Summary

This article explains how order book depth at increasing distances from the mid-price relates to execution costs. It defines 5, 10, and 50 basis point bands as nested regions of the book and explains that larger orders may consume liquidity farther from the midpoint, increasing average slippage. The suggested tier to monitor depends on order size and trading horizon: the innermost band for frequent, short-term trading, the middle band for building positions, and the widest band for large or strategy-driven orders.

Illustrative calculations compare estimated costs for deep and thin books across small frequent trades, a single position entry, and a large one-shot order. These examples show how per-trade differences can accumulate, but they are hypothetical estimates rather than measured venue data. Actual execution depends on order book conditions, order size, and market behavior; depth at a quoted band alone does not guarantee a particular fill price. The article’s practical lesson is to assess liquidity at the distances relevant to one’s expected trade size.

Key ideas

• Order book depth measures available liquidity at price levels around the mid-price.
• Larger orders can consume liquidity beyond the best quotes and incur greater slippage.
• Frequent short-term traders are especially sensitive to liquidity close to the midpoint.
• Position building and large orders may require monitoring wider depth bands.
• The article’s cost examples are illustrative and do not establish actual execution outcomes.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.