SMUG will identifies gaps and inconsistences between national social insurance and worker protection systems in terms of coverage, rule enforcement, and access, which increase the precarity of mobile workers. By definition, a posted work employment relationship is regulated in at least two European countries, possibly three. A major difficulty with regulating pan-European labour markets is that regulators and worker protection systems are tied to national jurisdictions and can only regulate a part of a posted workers’ employment relationship. Despite improvements in EU rule systems and transgovernmental cooperation, the overall effect of posting has been a haphazard deregulation, with firms exploiting regulatory gaps. This research will be based on the narratives of posted workers. Researchers will collect biographical interviews of posted workers to see how the interactions between national systems affect their welfare, and catalogue their economic coping strategies, so as focus on construction, because it where posting is best established.