This excerpt taken from the PCG 10-K filed Feb 18, 2005.
4.3. Targets for Availability Performance
The Availability Measure Targets described herein shall be phased in over a period of five years beginning on the ISO Operations Date. The adequacy of each PTO's Availability performance shall be monitored through the use of charts on which are plotted indices reflecting annual Availability performance. These charts, called control charts as shown in Figure 4.3.1, are defined by a horizontal axis with a scale of years and a vertical axis with a scale describing the expected range of magnitudes of the index in question. Annual performance indices shall be plotted on these charts and a series of tests may then be performed to assess the stability of annual performance, shifts in performance and longer term performance trends.
Control charts for each of the following indices shall be developed and utilized to monitor Availability performance for each Voltage Class within each PTO's system: