Apprentice and trainee data are reported by the State and Territory Training Authorities to NCVER (National Centre for Vocational Education Research) on a quarterly basis, starting at the September quarter of 1994. The set of data submitted that quarter is referred to as Collection 1. The sets of data submitted in subsequent quarters are referred to as Collection 2, Collection 3 and so on. NCVER publishes data on the numbers of contracts of training that commence, complete, cancel/withdraw, re-commence, expire or suspend and the time at which these events occur (referred to as the "date of effect"). From these events, the number of contracts in training at a given time can be calculated. Due to time delays in reporting data on the status of contracts to NCVER, the most recent data are estimated. Further details regarding this methodology are provided in the technical paper produced by NCVER, Estimation of Apprentice and Trainee Statistics, which can be found at http://www.ncver.edu.au/publications/2267.html. The purpose of this technical paper is to document the adjustments that are made to the estimates at each collection, and produce a cumulative document of these adjustments, commencing at Collection 60, June 2009 estimates. (Contains 15 figures.) [For the main report, "Australian Vocational Education and Training Statistics: Apprentices and Trainees. September Quarter, 2010", see ED516870.]