Transitions entre les secteurs formel et informel en période de crise au Vietnam

</titre> This paper contributes to fill the knowledge gap on the micro dynamics of the informal sector by addressing three issues : (1) transition patterns of household businesses between formal and informal sectors ; (2) factors associated with the decision of formalization, and (3) factors associated with the largely unknown process of informalization. It combines a unique panel data, representative of the Vietnamese urban informal sector, with a complementary qualitative research. The major result is that the informal sector plays simultaneously the role of buffer, informalization being essentially a cost-reduction strategy, and incubator, as more promising businesses choose to join the formal sector.