One form of ecological fallacy is found in the dictum that "you are where you live"--otherwise expressed in the idea that you can infer significant information about an individual or their family from the prevailing conditions around their home. One expression of this within higher education in the UK has been the use (and, arguably, overuse and misuse) of "low participation neighbourhoods" (LPNs) over the last 15 years. These are areas that have been defined, from historic official data, as having a lower-than-average propensity to send their young people on to university. These LPNs have increasingly become used within the widening participation and social mobility agendas as a proxy for young people from disadvantaged backgrounds who have the potential to benefit from higher education, but who would not attend without encouragement, support and/or incentives. In this article, we explore the various uses to which LPNs have been put by policy makers, universities and practitioners, including the targeting of outreach activities, the allocation of funding and the monitoring of the social mix within higher education. We use a range of official data to demonstrate that LPNs have a questionable diagnostic value, with more disadvantaged families living outside them than within them, while they contain a higher-than-expected proportion of relatively advantaged families. We also use content analysis of university policy documents to demonstrate that universities have adopted some questionable practices with regard to LPNs, although some of these are now being actively discouraged.