New Zealand Police Theft Proceedings Analysis

An R analysis of New Zealand Police offender proceedings data examining whether theft-related proceedings are disproportionately represented among younger age groups after accounting for each age group's total proceedings.

Raw counts answer where the greatest volume of theft proceedings occurs. Within-age proportions answer a different question: how prominent theft is within each age group's overall proceedings profile.

Using both avoids a misleading comparison between age groups with very different total numbers of proceedings.

• Ages 30-34 recorded the largest theft count, with 2,636 proceedings.
• Ages 15-19 recorded 2,547 theft proceedings.
• Ages 35-39 recorded 2,529 theft proceedings.
• After adjusting for each age group's total proceedings, ages 10-14 had the highest theft share at approximately 35%.
• Ages 15-19 had the next highest share at approximately 18%.

The results support the research question descriptively: theft is proportionally more prominent among the youngest offender age groups, even though adults in their thirties account for larger absolute counts.

.
|-- README.md
|-- requirements.R
|-- R/
|   `-- analysis.R
|-- data/
|   |-- LICENSE.md
|   |-- police_data.csv
|   `-- theft_age_group_summary.csv              # generated on execution
|-- report/
|   `-- nz_police_theft_proceedings_analysis.Rmd
`-- assets/
    |-- nz_police_theft_by_age_chart.png
    `-- nz_police_theft_proportion_chart.png

Use R 4.3 or newer.

source("requirements.R")

Run the data preparation and figure generation:

RUN_FULL_ANALYSIS=1 Rscript R/analysis.R

Render the report:

rmarkdown::render("report/nz_police_theft_proceedings_analysis.Rmd")

The workflow validates required columns, removes unspecified age categories, applies an ordered age factor, aggregates theft and all-offence proceedings, calculates within-age theft proportions, and checks selected reported values.

Source: New Zealand Police, Proceedings (offender demographics), 12-month reporting period April 2025 to March 2026.

New Zealand Police states that reports and data linked from policedata.nz are reusable under the Creative Commons Attribution 4.0 International Licence. Attribution details are recorded in data/LICENSE.md.

The export contains aggregate proceedings, not individual-level records. It must not be used to identify or speculate about individuals.

• Proceedings reflect offences recorded by Police and resulting in proceedings, not all theft in the community.
• A proceeding is not the same as a unique offender; one person may be associated with multiple proceedings.
• Age groups are aggregated, so the analysis cannot explain individual behaviour.
• Results are descriptive and do not show that age causes theft-related offending.
• The selected 12-month period is a snapshot and may not represent longer-term patterns.

R, R Markdown, readr, dplyr, ggplot2, grouped summaries, ordered categorical data, denominator-aware proportion analysis, reproducible reporting, public-data attribution, validation, and careful interpretation of justice data.