Previously, companies could structure many acquisition transactions to determine the choice between two accounting methods to record a business combination:
purchase accounting or pooling-of-interests accounting. Pooling-of-interests method combined the book value of assets and liabilities of the two companies to create the new balance sheet of the combined companies.
It therefore did not distinguish between who is buying whom. It also did not record the price the acquiring company had to pay for the acquisition.
Since 2001 US Generally Accepted Accounting Principles (FAS 141) no longer allows the pooling-of-interests method.