Purpose
This appendix explains how differences between police-recorded vehicle theft figures and DVLA stolen-vehicle notifications are calculated, including the exact formulas used, to avoid ambiguity or misinterpretation of percentages.
Data sources
- Police / Home Office recorded vehicle theft figures
Annual totals derived from police-recorded crime data (financial-year basis). - DVLA stolen-vehicle notifications
Annual totals of vehicles notified to DVLA as stolen (calendar-year basis).
Important note on periods:
Police/Home Office figures are typically reported on a financial-year basis, while DVLA figures are reported on a calendar-year basis. This mismatch is acknowledged and does not, by itself, explain the scale of the discrepancies observed.
Definitions
- HO = Home Office / police-recorded vehicle theft total
- DVLA = DVLA stolen-vehicle notification total
- Difference (Δ) = HO – DVLA
Formulas used
1. Absolute numerical difference
This measures the raw gap between the two datasets:
Δ = HO – DVLA
2. Percentage difference (DVLA-denominator)
This expresses how much lower the DVLA figure is relative to DVLA’s own total:
Percentage difference (DVLA-based) = (HO − DVLA) / DVLA × 100
This figure answers the question:
“By what percentage is the Home Office figure higher than the DVLA figure, relative to DVLA’s count?”
3. Percentage difference (HO-denominator) – provided for clarity
This expresses the proportion of police-recorded thefts not reflected in DVLA data:
Percentage difference (HO-based) = (HO − DVLA) / HO × 100
This figure answers the question:
“What proportion of police-recorded thefts do not appear in DVLA stolen-vehicle notifications?”
Example (illustrative)
If:
- HO = 126,810
- DVLA = 95,589
Then:
- Δ = 31,221
- DVLA-based difference = 32.66%
- HO-based difference = 24.62%
Interpretation
- DVLA-based percentages are used in this report when describing how much lower DVLA totals are compared with police totals.
- HO-based percentages are provided where clarity is required on the proportion of police-recorded thefts not reflected in DVLA records.
- Both are mathematically correct; the denominator must be stated explicitly.
