{
  "source": "cbbo_1m_recent",
  "n_days": 19,
  "hourly_median": {
    "09": 5.95,
    "10": 6.1,
    "11": 5.05,
    "12": 1.7,
    "13": 1.55,
    "14": 1.6,
    "15": 2.1,
    "16": 1.7
  },
  "description": "Median ATM bid-ask spread by ET hour, computed from 19 recent trading days",
  "note": "Hour keys are 2-digit ET hour strings (09, 10, ... 16)"
}