Preface: About the data

Where did we look for data?

Due to the scarcity of centralised data on immigration detention, we looked for data that exists under multiple government departments. Furthermore, the limited data on detention makes comparative data, such as with prison institutions, increasingly relevant.

What are the difficulties in finding data?

Thus, the difficulty of finding data on detainee population is in part due to the fact that detainees may be scattered across multiple institutions under the authority of multiple departments.

Another difficulty is that datasets that cover different time periods might not use the same measurement; this makes merging datasets to get a larger time period not possible.

Measurements and units

Data measures that have been used in the datasets we encountered include:

• yearly admittances,
• average daily population, and
• a snapshot of the population at a given date (ex. end of the month, end of the year)

Yearly admittances can illuminate the scale of turnover in a facility while average daily population could be useful to understand which years a facility is closer to capacity. However since average daily population would never exceed the capacity of the facility, a broader comparison between facilities may remain limited.

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