You mean corporations and their total capital? Total capital values and economical power were never listed (and, for megacorps, these numbers are probably going to be thousands of trillions of credits for the very least - these are companies operating over numerous sectors of space); however, the following corporations are listed:
S8: Library Data A-M
Delagdo Trading, LIC (Military Hardware, Mining, Heavy Industry)
General Products, LIC (Heavy Industry, Starships)
GSbAG (Starships, with big Imperial contracts, both for the Navy and the Emperor)
Hortalez et Cie, LIC (Financial Services)
Instellarms, LIC (Military Hardware, Mercenaries)
Ling Standard Products (Mining, Electronics, Starships, Vehicles, Consumer Goods, Small Arms)
Makhidkarun (Communicatiosn and Entertainment)
Naasirka (Electronics, Computers, Software)
SuSAG, LIC (Chemical Industry, Bio-Industry, Pharmaceuticals, Genetics)
Sharurshid (Trade and Speculation)
Sternmetal Horizons, LIC (Mining, Heavy Industry, Construction, Vehicles)
Tukera Lines, LIC (Transport)
Zirunkariish (Banking and Investment)
LBB8: Robots
Tlektaowa (Aslan: Robotics)
Star Patterns Trading (Hiver: Robotics)
SURD (Robotics Research)
Spinward Specialities (Robotics)
Kllkoog'x' (K'Kree: Cleaning Robots)
Panstellar (Solomani: Construction, Starships, Robotics)
Eksaekfoer (Vargr: Low-Grade Robotics)
A1: Kinunir
General Shipyards (Subsector-scale Starship Manufacturing)
A4: Leviathan
Baraccai Technum (Spinward Marches/Outer Rim Void Trading and Exploration)
McClellan Factors (Spinward Marches/Outer Rim Void Trading and Exploration)
Arkesh Spacer (Semi-Piratical Trading in the Marches)
DA2: Across the Bright Face
Dinom Corp (Mining on Dinom; overthrown/nationalized in 1160 by the Dinom Revolution)
Or do you mean military companies (i.e. the unit which is composed of 2-5 platoons) and their total sizes?
