dnb bank said monday that it has decided to begin a sharebuyback program comprising up to 15 of the companys own stock which represents a total of 231 million shares the buyback was adopted based on shareholder authorization given in april and will reduce the common equity tier 1 capital ratio by around 050 percentage points it said at the end of the second quarter of this year the company had a cet1 capital ratio of 189 dnb said the financial supervisory authority of norway has approved the buyback on the condition that the total buybacks dont reduce the companys own funds by more than 49 billion norwegian kroner 4876 million