Activating Voluntary Social Insurance Participation in Vietnam’s Informal Sector: An Integrated Theoretical Framework Synthesising Planned Behaviour and Self-Determination Theories

Expanding social insurance coverage to informal sector workers remains a critical challenge in emerging economies. This study advances theoretical understanding by proposing and empirically validating an innovative integrated framework that synthesises the Theory of Planned Behaviour (TPB) and Self-Determination Theory (SDT), addressing the limitations of single-theory approaches that inadequately explain the intention-behaviour gap in voluntary social insurance (VSI) participation. Whilst TPB elucidates cognitive determinants of intention formation, SDT enriches the model by capturing motivational quality underpinning sustained behaviour, representing a novel theoretical integration previously unexplored in informal sector financial protection contexts. Through structural equation modelling analysis of survey data from 800 informal workers across Vietnam’s six regions, this research empirically confirms traditional TPB relationships. It establishes intrinsic motivation as a direct predictor and crucial mediator between risk perception and intention—a previously unidentified psychological mechanism. Income demonstrates a paradoxical dual role, negatively affecting direct participation whilst positively moderating the intention-behaviour relationship, revealing how material constraints interact with psychological readiness in complex ways. The integrated model exhibits substantial explanatory power for both intention ( R 2 = .639) and participation ( R 2 = .564), significantly exceeding single-theory applications and substantially extending current theoretical understanding of voluntary financial behaviours. These findings demonstrate how the integration of cognitive and motivational perspectives creates synergistic theoretical advancement, offering valuable implications for policymakers seeking to bridge the alarming gap between Vietnam’s ambitious social protection targets (60% labour force participation by 2030) and current empirical reality (3.92% VSI participation), whilst providing insights for similar emerging economies confronting informal sector coverage challenges.