contract <sectors>
    production in shell industries, defense plants, airports, harbours,
    bridge heads, mines, gold mines, research institutes and technology
    centers can be contracted. You will be offered a price per production
    unit. If you accept, then you will earn money as appropriate when the
    sector is updated. If you decline, the sector is left uncontracted. The
    presence of a contract is indicated by a '$' in the census listing.
Doc: economics, sectors
Help: census, update