A Theory of Offending and Forecasting The Prison Population

1
A Theory of Offending and Forecasting The Prison
Population

• Christine Harper
• Economics and Resource Analysis
• Home Office England

2
Theory of Offending and Prison Population
Forecasts

• Dr MacLeods Theory
• Data Analysis
• Prison Population Forecasts
• Implications
• Current/ Possible Future work

3
Theory Of Offending

• Data from Offenders Index
• Suggested
• Constant Criminality
• 2 characteristics of offending behavior
• Proportion re-convicted after each previous
  conviction (high risk 0.82, low risk 0.3)
• Probability of being re-convicted in a 12 month
  period (high rate 0.9, low rate 0.25)

4
Theory of Offending

• Three groups with different offending
  Characteristics
• High Risk High Rate
• Low Risk Low Rate
• Third Group? (High Risk Low Rate)

5
Reconviction Probability
6
Offending Rate
7
Theory of Offending
8
Convictions by Age

• Using Theory
• Age at First Conviction
• First Observed Conviction
• Demographics
• Number of first time Convictions.
• Number of Re-Convictions.

9
Prison Model
10
Policy Inputs

• Sentence Lengths.
• Custody Rates.
• Remission

11
Prison Population Forecasts
12
Implications

• Theory Predicts Number of Convictions.
• Theory Implies that Certain Proportion give up
  after being Convicted
• Independent of Sentence.
• Independent of Number of Convictions.
• Crime Reduction?
• Policing Tactics?

13
Implications for Crime Reduction
Prison Population Increased by 25
14
Current Work/ Possible Future work

• Extension of theory to less serious convictions
  to enable prediction of other court sentences.
• Do these groups actually exist?
• Review of Prison and Probation Population
  Forecasts.