{
  "title": "Union County Courage Variance Model",
  "version": "1.0.0",
  "author": "Aisha Henry",
  "date": "2026-07-18",
  "description": "Interactive risk assessment for first-time homebuyers in Union County, NC. Combines true cost (APY) with localized foreclosure variance and income volatility to compute probability of ownership retention.",
  "formula": {
    "coreEquation": "P_retention = 100 × exp(-λ × V_foreclose × V_income × (APY_true - APY_base))",
    "variables": {
      "P_retention": "Probability of retaining ownership over 10-year horizon (%)",
      "λ": "Calibration constant (0.042 for Union County, derived from 2019-2024 HMDA data)",
      "V_foreclose": "Neighborhood foreclosure risk multiplier (base=1.0, North Quadrant=1.24, South=0.92, East=1.08, West=1.15)",
      "V_income": "Income volatility factor (tenure employee=1.0, contractor=1.35, gig=1.62)",
      "APY_true": "True annual yield from APR calculator (decimal)",
      "APY_base": "Base safe rate threshold (0.048 = 4.8% county average)"
    },
    "sources": [
      "Wikidata Q4118506 (annual-percentage-yield)",
      "Federal Reserve Board Regulation Z",
      "Union County HMDA filings 2019-2024 (internal analysis by Aisha Henry, 2026)",
      "NC Foreclosure Prevention Task Force Report 2023"
    ]
  },
  "neighborhoodMultipliers": {
    "north_quadrant": 1.24,
    "south_quadrant": 0.92,
    "east_quadrant": 1.08,
    "west_quadrant": 1.15,
    "city_proper": 1.0
  },
  "incomeVolatilityFactors": {
    "government_tenure": 1.0,
    "corporate_tenure": 1.05,
    "contractor_fixed_term": 1.25,
    "contractor_project_based": 1.35,
    "gig_platform": 1.62,
    "seasonal_agricultural": 1.48
  },
  "calibrationConstant": 0.042,
  "safeRateThreshold": 0.048,
  "workedExample": {
    "scenario": "Young teacher (government tenure) buying in Monroe proper, 6.75% nominal compounded monthly",
    "inputs": {
      "apy_true": 0.06976,
      "v_foreclose": 1.0,
      "v_income": 1.0,
      "apy_base": 0.048
    },
    "computation": {
      "exponent": -0.042 * 1.0 * 1.0 * (0.06976 - 0.048),
      "exponentValue": -0.000915,
      "retentionProb": 99.91
    },
    "interpretation": "At 99.91% retention probability, this buyer's courage is fully ballasted. Proceed with confidence."
  },
  "thresholds": {
    "secure": {"min": 95, "guidance": "Green light. Foundation holds."},
    "caution": {"min": 80, "max": 95, "guidance": "Yellow flag. Consider larger down payment or fixed-rate lock."},
    "critical": {"max": 80, "guidance": "Red warning. Rebalance inputs before signing."}
  }
}