Market Microstructure for Systematic Traders
Edge in modern markets is increasingly determined by execution. A primer on the structural features every systematic trader should understand.
A systematic strategy with a 1.5 Sharpe in research and a 0.6 Sharpe in production is not a victim of bad luck. It is almost always a victim of microstructure: bid-ask spreads, market impact, queue position, latency to the exchange, hidden liquidity dynamics and adverse selection.
Where impact actually comes from
Market impact has two components. Temporary impact moves price while you trade and reverts. Permanent impact reflects the information your order conveys to the market. Both scale roughly with the square root of size relative to average daily volume — the empirical “square-root law” that practitioners have replicated across asset classes.
Practical implications for backtests
Most academic backtests assume costless trading. Production performance lives or dies on cost modelling. A realistic transaction-cost model is non-linear in size, includes a spread component and an impact component, and is recalibrated against live execution data — not once at strategy launch.
Execution as a return driver
For higher-turnover strategies, execution quality is itself a meaningful source of edge. Volume-participation algorithms, implementation shortfall benchmarks, and venue-aware routing reduce slippage by meaningful basis points. Over a year of compounding, that is the difference between a viable strategy and a marginal one.
FAQ
Does microstructure matter for low-turnover strategies?
Less, but not zero. Even quarterly rebalanced factor portfolios benefit from intelligent execution scheduling.
Should systematic firms build or buy execution?
Most allocators buy. Most quant funds with meaningful turnover build at least the routing and TCA layer in-house.
August Quants Research
The August Quants research desk publishes educational essays on systematic investing, market structure, ML in finance and portfolio construction. We write for institutional readers who value rigour over noise.