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Prison Population

Background to Publication Delay

The delay in publication of the ‘Northern Ireland Prison Population’ series from 2011 onwards followed the discovery of a data anomaly in receptions information published in the ‘Northern Ireland Prison Population in 2009’. Specifically, information for prison receptions relating to the year 2009 in Tables 7-12 of that publication are not to be considered reliable. These figures represented a clear discontinuity with the data series for the years 2000-2008.

The source of this discontinuity for reception information was established as being the transition to a new and improved information management system (PRISM) within the Northern Ireland Prison Service, which became the source of statistical information for this publication for the first time for the calendar year 2009. It can be seen from the published 2009 data that the numbers of receptions were given as decreasing, in some cases dramatically, at a time when numbers on the whole were increasing. The reason for this was that the validation conducted on the dataset for the publication had failed to identify that in the process of migration to the new system, the traditional statistical base fields of the Custody History Section had not always been fully populated.

It was quickly established that there were no grounds for considering reception figures in these tables relating to the earlier years (2000-08) as other than reliable. Nor were there any grounds for doubting the accuracy of figures relating to average population itself, as contained in Tables 1-6 and related text.

Interim Publication

Pending resolution of receptions issue, it was originally decided to delay publication of subsequent NI Prison Population reports (which routinely comprised both population and reception information). While this was the correct decision regarding receptions information, it was not envisaged that this would be for the length of time that it finally involved. In addition, it also led to lack of public availability of average population figures themselves, when there was no reason to doubt their accuracy.

A user consultation exercise carried out in May/early June 2013 established that there was a desire among a substantial proportion of users for publication of an interim bulletin detailing the average prison population figures for the years 2010-2012. This would place these figures in the public domain without holding matters up further while the difficulties with receptions data were being addressed. This interim bulletin was published on 25 July 2013.

Latest Developments

Since the introduction of this new system considerable work has been carried out to ensure that full custodial history for each prisoner can be analysed. Following on from this, a statistical mechanism has also now been derived which should enable the compiling of statistics on receptions for each prisoner based on comparison of changes in daily snapshot information on prisoner population (i.e. to derive prisoner flow information from an analysis of daily changes in  population stocks).

A pilot test of this mechanism for data covering the year 2012 will be undertaken in December 2013. Depending on the outcome of this pilot, the intention would be that receptions figures for the years 2009-2012 inclusive should be available for publication by late spring 2014.

Population bulletins

Your views sought

Consultation of users on the longer-term structure and format of publications is being conducted primarily by a combination of a more in depth questionnaire to known users and stakeholders together with a limited number of group interviews. If you would be interested in inputting to this process, have any other comments you would wish to make or would simply like to register interest in being informed of further publications, please Contact us .