{
  "_readme": "Construction Cost Estimator data (Phase 3). Planning estimate only, never a bid. Base $/sq ft and stage shares from the NAHB Cost of Constructing a Home 2024 study; regional medians from NAHB's analysis of the Census Survey of Construction. The quality and foundation blocks are Zainfy ASSUMPTIONS by design (SPEC) — the UI must label them 'assumption', never 'data'. Refresh as_of when NAHB publishes the 2026 survey.",
  "base": {
    "avg_cost": {
      "value": 428215,
      "source": "NAHB Cost of Constructing a Home in 2024",
      "source_url": "https://eyeonhousing.org/2025/01/cost-of-constructing-a-home-in-2024/",
      "as_of": "2025-01"
    },
    "avg_sqft": {
      "value": 2647,
      "source": "NAHB Cost of Constructing a Home in 2024",
      "source_url": "https://eyeonhousing.org/2025/01/cost-of-constructing-a-home-in-2024/",
      "as_of": "2025-01"
    },
    "study_url": "https://www.nahb.org/news-and-economics/housing-economics-plus/special-studies/special-studies-pages/cost-of-constructing-a-home-in-2024",
    "note": "cost_per_sqft is DERIVED in the module as avg_cost / avg_sqft (~$161.77) — never typed anywhere."
  },
  "stages": {
    "source": "NAHB Cost of Constructing a Home in 2024, Table 3 (share of construction cost)",
    "source_url": "https://eyeonhousing.org/2025/01/cost-of-constructing-a-home-in-2024/",
    "as_of": "2025-01",
    "list": [
      { "stage": "Site work",              "pct": 7.6 },
      { "stage": "Foundations",            "pct": 10.5 },
      { "stage": "Framing",                "pct": 16.6 },
      { "stage": "Exterior finishes",      "pct": 13.4 },
      { "stage": "Major systems rough-ins","pct": 19.2 },
      { "stage": "Interior finishes",      "pct": 24.1 },
      { "stage": "Final steps",            "pct": 6.5 },
      { "stage": "Other",                  "pct": 2.1 }
    ]
  },
  "regional": {
    "source": "NAHB Eye on Housing — Square Foot Prices Moderate in 2024 (Census Survey of Construction, homes started 2024; median contract price per sq ft, contractor-built custom single-family, excluding lot)",
    "source_url": "https://eyeonhousing.org/2025/10/square-foot-prices-moderate-in-2024/",
    "as_of": "2025-10",
    "national_median_ppsf": 166,
    "division_median_ppsf": {
      "New England": 190,
      "Middle Atlantic": 188,
      "East North Central": 186,
      "West North Central": null,
      "South Atlantic": 155,
      "East South Central": 129,
      "West South Central": 138,
      "Mountain": 169,
      "Pacific": 167
    },
    "note": "West North Central custom-home median not published (insufficient sample) — module falls back to a 1.00 multiplier and says so. Multiplier is DERIVED as division ÷ national, never typed."
  },
  "state_to_division": {
    "source": "U.S. Census Bureau — Census Regions and Divisions of the United States",
    "source_url": "https://www.census.gov/programs-surveys/economic-census/guidance-geographies/levels.html",
    "as_of": "2025",
    "map": {
      "CT": "New England", "ME": "New England", "MA": "New England", "NH": "New England", "RI": "New England", "VT": "New England",
      "NJ": "Middle Atlantic", "NY": "Middle Atlantic", "PA": "Middle Atlantic",
      "IL": "East North Central", "IN": "East North Central", "MI": "East North Central", "OH": "East North Central", "WI": "East North Central",
      "IA": "West North Central", "KS": "West North Central", "MN": "West North Central", "MO": "West North Central", "NE": "West North Central", "ND": "West North Central", "SD": "West North Central",
      "DE": "South Atlantic", "DC": "South Atlantic", "FL": "South Atlantic", "GA": "South Atlantic", "MD": "South Atlantic", "NC": "South Atlantic", "SC": "South Atlantic", "VA": "South Atlantic", "WV": "South Atlantic",
      "AL": "East South Central", "KY": "East South Central", "MS": "East South Central", "TN": "East South Central",
      "AR": "West South Central", "LA": "West South Central", "OK": "West South Central", "TX": "West South Central",
      "AZ": "Mountain", "CO": "Mountain", "ID": "Mountain", "MT": "Mountain", "NV": "Mountain", "NM": "Mountain", "UT": "Mountain", "WY": "Mountain",
      "AK": "Pacific", "CA": "Pacific", "HI": "Pacific", "OR": "Pacific", "WA": "Pacific"
    },
    "names": {
      "AL": "Alabama", "AK": "Alaska", "AZ": "Arizona", "AR": "Arkansas", "CA": "California", "CO": "Colorado", "CT": "Connecticut",
      "DE": "Delaware", "DC": "District of Columbia", "FL": "Florida", "GA": "Georgia", "HI": "Hawaii", "ID": "Idaho", "IL": "Illinois",
      "IN": "Indiana", "IA": "Iowa", "KS": "Kansas", "KY": "Kentucky", "LA": "Louisiana", "ME": "Maine", "MD": "Maryland",
      "MA": "Massachusetts", "MI": "Michigan", "MN": "Minnesota", "MS": "Mississippi", "MO": "Missouri", "MT": "Montana",
      "NE": "Nebraska", "NV": "Nevada", "NH": "New Hampshire", "NJ": "New Jersey", "NM": "New Mexico", "NY": "New York",
      "NC": "North Carolina", "ND": "North Dakota", "OH": "Ohio", "OK": "Oklahoma", "OR": "Oregon", "PA": "Pennsylvania",
      "RI": "Rhode Island", "SC": "South Carolina", "SD": "South Dakota", "TN": "Tennessee", "TX": "Texas", "UT": "Utah",
      "VT": "Vermont", "VA": "Virginia", "WA": "Washington", "WV": "West Virginia", "WI": "Wisconsin", "WY": "Wyoming"
    }
  },
  "assumptions": {
    "_label": "Zainfy assumptions, NOT survey data — the UI must say 'assumption'",
    "quality_multiplier": { "economy": 0.8, "standard": 1.0, "custom": 1.4 },
    "foundation_adder_ppsf": { "slab": 0, "crawl": 3, "basement": 12 },
    "range_pct": 10,
    "gc_op_default_pct": 20,
    "gc_op_band_pct": [15, 25]
  }
}