{
  "simulated": true,
  "firm_id": "five-digit text identifier; preserve leading zeros",
  "year": "four-digit year",
  "revenue": "nonnegative number with optional correctly grouped thousands commas; blank means missing; simulated units",
  "employees": "nonnegative integer; blank means missing",
  "region": "nonempty text label",
  "source_row": "immutable row provenance for the master table",
  "lookup_row": "immutable row provenance for the lookup table"
}