Before the Commerce Amendment Act came into force, the Commerce Commission was required to set thresholds and assess the performance of lines businesses against those thresholds.
The Commission's first threshold period covered August 2001 to March 2004. For Transpower it was August 2001 to June 2004.
A new price period (implemented in December 2003) covered the regulatory period of five years beginning on 1 April 2004 of 31 March 2009. Transpower had a one year threshold from 1 July 2004 to 30 June 2005.
In effect, the thresholds were a screening mechanism to identify lines businesses whose performance required further examination. If one or more of the (price or quality) thresholds were breached by a lines business, the Commission could further examine the business through a post-breach inquiry and, if required, control their prices, revenue or quality.
