def evaluate_blocking(records, ground_truth_pairs, blocking_fn):
    candidates = blocking_fn(records)
    true_matches = set(ground_truth_pairs)
    found = candidates & true_matches
    missed = true_matches - candidates
    recall = len(found) / len(true_matches) if true_matches else 0.0
    reduction_ratio = 1.0 - len(candidates) / (len(records) * (len(records) - 1) / 2)
    return {
        "recall": recall,
        "candidate_pairs": len(candidates),
        "reduction_ratio": reduction_ratio,
        "missed_true_matches": len(missed),
    }

# Name-only blocking:   recall 0.73, candidate_pairs 42_000, missed 12_500
# Composite blocking:   recall 0.94, candidate_pairs 59_000, missed 2_800