This announcement has received wide coverage in the financial press, with speculation about oil futures price manipulation.
Officials said investigations were continuing into possible price manipulation and collusion among the companies.
They call for listed companies to have at least 1,000 shareholders of record, which makes price manipulation more difficult.
They have urged an investigation into possible price manipulation.
"Those who claimed that there was no price manipulation here were just plain wrong."
The biggest case so far, involving price manipulation of a new stock issue, dates back to 1972.
Still, he sees no evidence now of price manipulation among the Big Three.
With only seven suppliers, price manipulation may also be at work.
Con Ed says it has already taken into account the possibility of price manipulation.
It is because of this increase that we are calling for urgent measures to combat price manipulation.
Wörterbuch für Wirtschaftswissenschaft