The daily rhythms of the city, the ebb and flow of people undertaking routines activities, inform the spatial and temporal patterning of crime. Being able to capture citizen mobility and delineate a crime-specific population denominator is a vital prerequisite of the endeavour to both explain and address crime. This paper introduces the concept of an exposed population-at-risk, defined as the mix of residents and non-residents who may play an active role as an offender, victim or guardian in a specific crime type, present in a spatial unit at a given time. This definition is deployed to determine the exposed population-at-risk for violent crime, associated with the night-time economy, in public spaces. Through integrating census data with mobile phone data and utilising fine-grained temporal and spatial violent crime data, the paper demonstrates the value of deploying an exposed (over an ambient) population-at-risk denominator to determine violent crime in public space hotspots on Saturday nights in Greater Manchester (UK). In doing so, the paper illuminates that as violent crime in public space rises, over the course of a Saturday evening, the exposed population-at-risk falls, implying a shifting propensity of the exposed population-at-risk to perform active roles as offenders, victims and/or guardians. The paper concludes with a discussion of the theoretical and policy relevance of these findings.

城市的日常节奏、日常活动的潮起潮落，为犯罪的时空格局提供信息。能够捕捉公民的流动性并描绘特定犯罪的人口分母是努力解释和解决犯罪的重要先决条件。本文介绍了暴露的高危人群的概念，其定义为居民和非居民的组合，他们可能在特定犯罪类型中作为罪犯、受害者或监护人发挥积极作用，在给定时间以空间单位存在。该定义用于确定公共场所与夜间经济相关的暴力犯罪风险暴露人群。通过将人口普查数据与手机数据相结合，并利用细粒度的时空暴力犯罪数据，本文展示了部署暴露的（在环境上的）高危人群来确定周六公共空间热点暴力犯罪的价值在大曼彻斯特（英国）过夜。在这样做的过程中，该论文阐明，随着公共场所暴力犯罪的增加，在周六晚上的过程中，暴露的高危人群下降，这意味着暴露的高危人群的倾向发生转变，发挥积极作用，如罪犯、受害者和/或监护人。