The "top 50" list of independent European plastic pipe extruders published by Applied Market Information Ltd. (AMI, www.amiplastics.com) has seen major changes since the last "Corporate Performance and Ownership among plastics pipe extruders - A Review of Europe's 50 Largest Players" was published in 2000. Less than 40 of the companies listed appear again in 2004, the Bristol-based research group says. Although mergers and acquisitions are partly responsible, AMI notes that three major multinational groups - Wavin (www.wavin.com) Zwolle / The Netherlands, Pipelife (www.pipelife.com), Enkhuizen / The Netherlands and Uponor (www.uponor.com), Vantaa / Finland - "have moved fast to maintain their dominance of this market."