[Update 15 April 2014: Scroll down to comments for a more detailed explanation of why the statistical report is flawed.]
The basis for Enfield Council’s private rented sector licensing proposal is quantitative research conducted by Mayhew Harper Associates (MHA/NKM), which has attempted to establish a link between the private rented sector and anti-social behaviour. This has been combined with qualitative research (focus groups etc.) run by Opinion Research Services (ORS) to identify the need.
The executive summary of the ORS report (full report not available) states at paragraph 1.12 that:
In the residents’ forums opinion was divided over whether there is a link between the PRS and ASB or whether problems were simply the result of an overall increase in population.
[PRS: private rented sector; ASB: anti-social behaviour]
The MHA/NKM report is based on modelled data which has attempted to predict which houses are in the private sector (either single family dwellings or houses in multiple occupation). No validation results are presented (assuming, I hope, that some was done).
The report does not include a comparison of anti-social behaviour for different tenure types (private rented, social rented, owner-occupier). The one straight line chart presented covers only modelled single family dwellings and does not even have a statistical value displayed to show the strength (or weakness) of the correlation (the R2 coefficient).
The Council also used maps produced from the modelled data as evidence of a correlation. They overlaid modelled PRS home locations on ASB rate maps:
What they didn’t do was any kind of comparison with the other social determinants of crime. I looked at Enfield’s own public health website and obtained this map of the index of multiple deprivation by ward:
This replicates their map quite well (partly because one of the deprivation factors is crime rate). This shows that there is probably more than one underlying driver of anti-social behaviour. There is also a stark west-east divide, with the dividing line being the route of the A10 road.
Even if MHA/NKM could demonstrate a simple correlation with just one factor (tenure type), this is not proof of causation. The report itself acknowledges that:
Note that because we have not uniquely ascribed ASB to individual households (for reasons previously given) this does not necessarily demonstrate cause and effect.
I question the basis for their conclusion that:
Enfield Council’s hypothesis that privately rented properties are associated with high levels of ASB also appears to have reasonable justification. In the limited instances where addresses were linkable, higher than average percentages of ASB were attributable to higher risk privately rented households.
In an earlier section they find that “statistically the correlation is weak”, so their conclusion seems baseless. They were only able to link ASB incidents to addresses in about 5% of cases, so the final sentence should be disregarded. Their conclusions are not supported by their own work and yet they have managed to make this bold claim, which Enfield Council have used to underpin their policy.