Factors Affecting Illegal Migration to the UK by Small-Boat Crossing of the English Channel: Descriptive, Inferential and Predictive Analyses

Small-boat crossing of the English Channel is a relatively new phenomenon, with relatively sporadic attempts prior to 2020 preceding the 148,998 migrant arrivals in the five years since. While this has elevated the issue to a major political priority in the UK, little remains known about the factors which influence the number of crossings. This IMR Dispatch from the Field combines various sources of public data to calibrate a statistical model for explaining daily migrant arrivals along this route. To account for a preponderance of zero-arrival days and overdispersion, a zero-inflated negative binomial regression was used. This essentially composes two models. The first estimates the probability of a day being ‘viable’ (possible for crossings to occur) and quantifies – for the first time – the specific contributions of wave height, sea temperature, and wind direction and speed. The second model estimates the number of migrant arrivals on such viable days, revealing – alongside weather-related effects – the impact of past EU illegal immigration (affecting the candidate pool) and new and defunct migrant-return agreements (representing deterrents). Plausible associations with other variables were also identified, although they did not achieve statistical significance. In addition to the inferential analysis, predictive modelling of several hypothetical scenarios for 2025 was also performed. Reported insights may have value at an operational level in supporting intelligent deployment of enforcement agencies based on forecasted conditions, and at a strategic level in guiding government policy based on evidenced deterrents.