Countries at similar income levels exhibit markedly different rates and anatomies of labor informality. We organize these patterns around three interacting forces: a legal wedge (minimum wages and non-wage labor costs, alongside enforcement), the sectoral productivity and composition, and the private value of formality (coverage, portability, and contract enforceability). A parsimonious model yields sharp “thin-margin” predictions: effects concentrate where earnings cluster near the minimum legal standards. Evidence from a cross-country, country–sector panel supports the framework—legal and enforcement effects are largest where thin-margin exposure is high; higher private value lowers informality and dampens wedge effects; and composition, especially within services, conditions aggregates. The results reconcile disparate findings and imply targeted policy: align enforcement with thin-margin exposure, raise the private value of formality via low-friction administration and portability, and pursue sectoral paths that expand formal-leaning activities.
