You have a company, at the start of the game you own 40% of the shares with 60% free to buy. Once all the shares in a company have been bought in order to buy that company (you gain their railroads and its game over for them) you have to buy out all the shares you dont own in one go. So if you own 70% of another company you have to buy the remaining 30% in one go, if you own 30% its the 70% you have to buy. Stupidly though if you buy all of your own shares you can still be bought out, which is just insane as why would you? and why should it be game over? if your company is bought for $50 million why cant you buy a rival who is priced at $30 million. Its a stupid crappy system