This excerpt taken from the PBR 6-K filed Aug 21, 2007.
18.2. Share grouping in terms of ADRs
On May 11, 2007 the Board of Directors approved the change in the ratio between the shares that it issues and American Depositary Receipts ADRs, from the present 4 (four) shares per ADR, to 2 (two) shares per ADR.
The objective of this change in the ADR ratio is to make it easier for the small investor to buy ADRs on the New York Stock Exchange NYSE and, consequently, increase the shareholder base. It also demonstrates the Companys confidence in its future results.
This change in the ADR ratio came into effect on July 02, 2007.