Opaque windows, hidden patterns? A layered analysis of erotic-service traces, corporate structure and property ownership in Chinese-linked massage centres in the Province of Milan

Research on indoor sexual-service markets faces a measurement problem: venues potentially hosting erotic services often appear as ordinary businesses, while ob-servable traces remain uneven. This study analyses 198 Chinese-linked massage centres in the Province of Milan, classified into three mutually exclusive groups: direct advertising traces, corroborative user-generated traces without direct ad-vertising, and no comparable traces in the selected sources and period. It com-pares coded indicators across venue presentation, corporate structure and proper-ty ownership. Visible venue features provide the clearest signals, while corporate and property data are weaker but useful. The study advances a layered, uncertain-ty-aware method for analysing semi-hidden markets.