The following four chapters assess the evidence for the relative performance of public and contracted prisons. They do so against the aims that have variously been stated for competition, namely that the private sector would:

• • provide a better service

• • operate at lower cost

• • build quicker and more cheaply, with better designs.

These chapters do not include youth justice, given the conclusion in Chapter 4 that there was very little competition between sectors. Where comparative data is available, contracted prisons in Scotland are included.

There is a considerable literature on comparing public and private custody, here and internationally. Comparisons are of course very far from straightforward, for many reasons.

• 1. Comparisons may be skewed by differences in prison size, function and prisoner mix. Age and design of building and (for cost) location may also affect results. Few studies attempt to match prisons to allow for such factors and matching is never perfect.

• 2. Comparisons may yield different results at different time: what was true in the 1990s may not be true now.

• 3. There may be differences within each sector as well as between sectors.

• 4. Measuring the quality of complex services such as prisons, with multiple and sometimes conflicting aims, is notoriously difficult.

• 5. Data may be unavailable, unclear, unreliable or inconsistent.

The approach throughout is less to argue what the perfect comparative data might be than to assess the evidence which does exist, and suggest what conclusions can reasonably be drawn from it, however limited and caveated.

Most of the analysis here is about cost. Harding (2001) argues there has been ‘disproportionate’ focus on cost in comparing sectors. On the contrary, there has been too little, at least in the UK. There is far better evidence for, and much greater agreement on, comparative quality of service than on comparative cost. Government has published no comparative study of the actual cost of public and contracted prisons since 1999 – and that was for only for one type of contract, which applies only to a small minority of privately run prisons.

Part of the reason may be that writing about prison is mostly by criminologists, whose professional culture is somewhat left of centre and who seem uneasy about the very notions of cost reduction, efficiency and competition.