Reliability of rating is assured through the face-to-face training and certification of examiners, and all must undergo a retraining and recertification process every two years. A Professional Support Network (PSN) manages and standardises the examiner cadre, including face-to-face examiner monitoring as well as distance monitoring (using recordings of the Speaking tests). A ‘jagged profile’ system maintains a further check on the global reliability of IELTS performance assessment. Routine targeted double marking identifies the level of divergence (i.e. jagged profile) between Writing and/or Speaking scores and Reading and Listening scores. This process allows for the identification of possible misclassified candidates. The jagged profile system is also combined with ‘targeted sample monitoring’ to further identify possible faulty ratings by examiners. Selected centres worldwide are required to provide a sample of examiners' marked tapes and scripts. Tapes and scripts are then second-marked by a team of IELTS Principal Examiners and assistant Principal Examiners. Principal Examiners monitor for quality of both test conduct and rating, and feedback is returned to each test centre. The outcomes that emerge from these reliability measures feed back into examiner retraining and continually build on quality management and assurance systems for IELTS.