By the end of 2000 PDO witnessed an increase in production. This was due to the increase in production arose from the application of the latest technology to increase oil recovery in existing fields. And some of the production increase over the years was made up of "new oil" from fields that were not only found but also developed at an ever-accelerating pace. During the period 1967–1980 all of PDO's production came from 11 fields; by 1988, 50 fields provided the sum total of PDO's oil output; by 1990 it was 60, and in 1999 it was nearly 100.