This is a brilliantly simple experiment: - most HFT companies use microwave transmitters because they are faster than fiber; - microwaves are disrupted by hea

This is a brilliantly simple experiment: - most HFT companies use microwave transmitters because they are faster than fiber; - microwaves are disrupted by heavy rain and snow, so they fall back to fiber; - one can observe bid-ask spreads when it rains to see how liquidity is affected. Conclusion: spreads narrow, and liquidity is improved when the fastest HFT traders are slowed down.