Matched cohort, 1,280 young people, administrative records

Criminology research poster example

A matched cohort study of youth diversion and twelve month reoffending, laid out as a classic A0 portrait research board. Three key numbers sit across the top of the results, and every one of them can be traced back to a count in the flow below.

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BU
Youth diversion and reoffending at twelve months: 1,280 matched young people
A. Sultana ¹, K. Marlowe ¹ ², J. Petrakis ²
1 School of Criminology, Barrowfield University · 2 Youth Justice Data Unit, Barrowfield University
Abstract
Police in this jurisdiction may divert a young person to a community programme instead of laying a charge, and the decision sits with the individual officer. We asked whether diversion is followed by less reoffending than a court appearance for young people who look alike on paper. Using administrative records for 1,912 eligible young people aged 12 to 17, we propensity matched 640 diverted to 640 court processed cases on age, prior contacts, offence category, postcode disadvantage and time of year. Within twelve months 122 of the diverted group and 198 of the court group had a further proven offence, which is 19% against 31%.
Background
Diversion is cheap, fast and popular with police, and the case for it usually rests on the cost saving rather than on outcomes. The outcome argument is harder to make because the young people who get diverted are not the young people who get charged: officers divert the ones they judge least likely to come back, which builds the answer into the sample. Matching does not solve that, but it narrows it to the factors an officer can actually see in the record, and it lets the size of any remaining bias be argued about openly rather than assumed away.
METHODS
Design. Retrospective cohort built from administrative records, propensity matched one to one, with twelve months of follow up from the diversion decision or the court date.
Population. All 1,912 young people aged 12 to 17 recorded as eligible for diversion across three financial years in one jurisdiction.
Matching. Nearest neighbour on age, prior contacts, offence category, postcode disadvantage decile and time of year, matched without replacement.
Outcome. Any further proven offence within 365 days, taken from the same administrative records rather than from self report or from police contacts.
Analysis. Risk difference with bootstrap confidence intervals over 2,000 resamples, with matched pairs resampled together so the pairing is preserved.
Data and thanks
Record linkage was carried out by the state data custodian under a research agreement; the authors saw no identified data at any stage. Two youth workers reviewed the offence categories and flagged three that mix summary and indictable matters; those were kept separate in the matching. The study was funded by the university and no funder saw the results before submission.
Twelve month outcomes
19%
reoffended after diversion
122 of 640 within twelve months
31%
reoffended after court
198 of 640 within twelve months
12 points
lower reoffending after diversion
95% CI 7.1 to 16.9, 1,280 matched young people
%
Div
Court
08162432
Figure 1. Proven reoffending within twelve months: Div diverted, Court processed through the childrens court.
Source: matched administrative records, three financial years.
PARTICIPANT FLOW
Young people eligible for diversion
1,912
Records incomplete
388
Complete records available
1,524
Outside the age range at decision
244
Available for matching
1,280
Matched pairs, one diverted and one court
640
Results
The 12 point gap holds in both prior offence strata and does not depend on any single year of the cohort. Pairs matched within the same postcode decile show the same difference as the full set. Half of the reoffending in the diverted group had happened by month six.
Reoffended
015304560
First offence, diverted
First offence, court
Prior offence, diverted
Prior offence, court
Figure 2. Reoffending by prior record and pathway, the four matched subgroups.
Source: matched administrative records, 1,280 young people.
%
3
6
9
12
05101520
Figure 3. Cumulative reoffending in the diverted group by month of follow up.
Source: 640 diverted young people, proven offences only.
Discussion
Twelve points is large enough to matter and small enough to be eaten by selection if officers can see something the record cannot. The subgroup pattern argues against that reading, because a hidden judgement about risk should shrink the gap among young people with a record rather than widen it.
Subgroups
Splitting by prior record: of 384 first offence pairs, 50 diverted and 92 court young people reoffended, which is 13.0% against 24.0%. Of 256 pairs with a prior offence, 72 and 106 reoffended, 28.1% against 41.4%. The gap is wider in absolute terms among those with a record.
What would settle it
Two designs would narrow the selection problem further. The first is a discontinuity: officers in this jurisdiction follow a scoring tool with a hard cut off, and young people either side of the cut off are close to randomly assigned. The second is a trial of assignment by roster rather than by officer judgement in the two districts where both pathways are equally resourced. Either would answer the question this design can only bound, and both are cheaper than the cost difference between the two pathways over a single year.
Conclusion
Among matched young people, diversion was followed by proven reoffending 12 percentage points lower than a court appearance, and the difference was present in both prior record groups. Selection on what an officer can see has been matched away; selection on what an officer can sense has not.
19% reoffended after diversion, 122 of 640
31% reoffended after court, 198 of 640
Gap 12 points, 95% CI 7.1 to 16.9
Present in both first offence and prior offence pairs
REFERENCES
1.Eldridge, T. and Marlowe, K. (2025) Matching on the visible record in youth justice research. Journal of Criminological Methods, 14(2), 177 to 201.
2.Nakamura, Y. (2024) Diversion programmes and proven reoffending: a review of cohort designs. Youth Justice Review, 31(1), 8 to 34.
3.Petrakis, J. (2026) Officer discretion at the diversion threshold. Barrowfield Criminology Working Paper 2026-01.

Block by block

What each block on the board is for, in the order a reader walks it.

Title band, three authors and a QR code
The title gives the comparison and the sample size: youth diversion and reoffending at twelve months across 1,280 matched young people. Three authors carry generated superscripts over two affiliations, with the QR code at the right of the band.
Abstract and background
The abstract states the design, the matching variables and both outcomes. The background explains why the comparison is hard: officers divert the young people they judge least likely to return, which builds the answer into the sample unless it is matched away.
Methods as a labelled protocol
Five entries: a retrospective matched cohort from administrative records, 1,912 eligible young people aged 12 to 17, one to one nearest neighbour matching on five variables, any proven offence within 365 days as the outcome, and bootstrap intervals over 2,000 resamples.
Three key numbers
Nineteen per cent reoffended after diversion, 122 of 640. Thirty one per cent reoffended after court, 198 of 640. The difference is 12 percentage points with a 95% confidence interval of 7.1 to 16.9 across 1,280 matched young people.
Matching flow
A flow with exclusions branching to the side: 1,912 eligible, 388 with incomplete records, 1,524 complete, 244 outside the age range at the decision, 1,280 available for matching and 640 pairs formed, one diverted and one court processed.
Three figures
Reoffending by pathway as two bars, the four matched subgroups as a horizontal bar chart running from 13.0% to 41.4%, and cumulative reoffending in the diverted group at three, six, nine and twelve months, reaching the same 19.1%.
Subgroups, discussion and what would settle it
The subgroup block gives the counts behind the figure. The discussion weighs selection against the subgroup pattern, and a future work block proposes a discontinuity design at the scoring cut off and a roster based assignment trial in two districts.

What makes this board work

Three numbers, each with its denominator

The board leads with 19%, 31% and 12 points, and every one carries the count it came from underneath. A percentage with no denominator is the most common fault on a real criminology board and the first thing a reviewer challenges.

The matching flow is shown, not described

1,912 eligible, 388 with incomplete records, 1,524 complete, 244 outside the age range, 1,280 available and 640 matched pairs. Every subtraction holds, which is what makes the sample claim checkable in ten seconds.

The limit is stated where it belongs

The discussion says plainly that matching removes selection on what an officer can see and not on what an officer can sense, and the subgroup figure is offered as the argument against that reading rather than as proof.

Questions people ask

What goes on a criminology research poster?

The policy question, the population and how the comparison group was built, the outcome and its follow up window, the headline difference with an interval, a flow that shows who was excluded, and at least one subgroup split. Administrative record studies stand or fall on the exclusions, so show them.

How do I show a matched design on a poster?

Use a flow diagram. It converts a paragraph about eligibility, missing records and matching into five boxes a reader checks by subtraction. Keep exclusions to the side of the spine so the main path still reads top to bottom, and make sure every number adds up.

How many figures fit on an A0 portrait board?

Three is comfortable on a classic research layout like this one, which carries reoffending by pathway, the four matched subgroups and cumulative reoffending by month. More than four and each one shrinks below the size where it can be read from a metre away.

What text size should I use for a poster?

Body text on this board sits near 24 pixels on a 1656 by 2340 canvas, about 12 millimetres printed at A0, which reads at a metre. Section headings are roughly double. If a block will not fit at that size, cut words rather than shrinking the type.

Can I print an A0 poster at 300 DPI from this?

The export doubles the working canvas, so A0 portrait comes out at 3312 by 4680 pixels, about 100 DPI at full size. That is the normal working resolution for a poster viewed from a metre. There is no bleed, no crop marks and no CMYK conversion.

How do I adapt this board to my own study?

Retype the title, authors and abstract, replace the five method entries, change the flow node labels and counts, and retype the three key numbers with your own denominators. Each figure holds its own data table, and the chart type can be switched from a list of ten.

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