Stat Juking revisited

By Eric Crampton 16/07/2014


I’d reckoned you’d need a bit of stats-fu to find evidence of police juking of the crime statistics. Turns out there was an easier way. Bevan Hurley reports that the Herald on Sunday got a copy of a report showing that Counties Manukau police had been fiddling the burglary numbers by recoding burglaries as less serious offences. 

About 700 burglaries were “recoded” in the Counties Manukau south area over three years, an internal police investigation has found. It found that about 70 per cent of the time, the offences should have remained burglaries.

The revelations will be an embarrassment for Police Commissioner Mike Bush, who was district commander of the area at the time, although he was not responsible for overseeing the coding.

Police have not said why the statistics were altered, but say staff were not under instruction to do so. Tolley denied police were under political pressure to reduce burglary statistics.

You don’t need overt political pressure to get this kind of outcome, just KPIs with strong enough incentives. On the plus side, they were caught. On the down side, I can’t see how lower level staff doing the coding would have any incentive to muck the stats around unless they were getting pushed by those whose KPIs did provide such incentive. It would be really interesting to read the full report.

The review listed dozens of examples where break-ins and attempted burglaries were downgraded, including one case where police failed to follow up after a witness gave them a burglar’s registration number.

The review found the burglary recoding rates in Counties Manukau south at the time were 15 per cent to 30 per cent whereas other areas typically recoded about 5 per cent.

So where last week’s rumours were about failing to pursue charges, which wouldn’t have mattered for stats based on recorded complaints, downgrading the complaints to less serious offences would matter.

I’d be curious to know what kinds of lesser offences were artificially inflated to keep the burglary numbers down.

I hope that the Police stats units have informed any researchers who’d been using the incorrect figures of the updated and corrected series. Anything that relied too heavily on 2009-2012 Manukau data is now going to have to be re-done.

The Herald on Sunday broke the story on the 13th. Their version is gated. The Stuff version, which notes “It was reported” rather than crediting the Herald, is here.

Update: Commenters over at Offsetting Behaviour, where I posted this a couple days ago, made the entirely reasonable point that what looks like target-based juking can also just be the result of police not wanting to bother pursuing burglary investigations in cases where it’s really unlikely that there’ll be any positive resolution and where they’ve other things they want to do. To distinguish time constraints from target constraints, we’d have to look for patterns in the improper recoding data. I’d expect a time-constrained department to have more improper recording of low-margin offences (offences where the return to more time investigating is low) where overall pressures from other crimes are binding, and a juking department to have more improper recording of particular offences when those offences’ rates are getting in excess of national norms. A juking department’s rate of improper classification will be sensitive to other departments’ crime rates; a time constrained one’s won’t be. I’d file this under potential future honours projects were I still in that game.