Matching Strategies

Standard vs Exhaustive Matching

• Standard (exhaustive_matching=False): uses nearest-neighbor style control selection with configurable method/replacement behavior.

• Exhaustive (exhaustive_matching=True): prioritizes wider control utilization while still respecting threshold constraints.

Key Parameters

• threshold: max allowed score distance

• nmatches: controls per treated unit

• replacement: whether a control can be reused

• method: "min" (closest) or "random" (random within threshold)

Practical Guidance

• Start with nmatches=1, replacement=False, and a moderate threshold.

• If retention is too low, loosen threshold gradually.

• If balance is weak after matching, tighten threshold or change model/balance strategy.

• For severe class imbalance, test balance_strategy="under" as sensitivity analysis.