Different methodological approaches applied in the literature to measure the magnitude of informal sector

The informal sector, which escapes from the national statistical account, grows very quickly and becomes more and more significance in the economy. Before summarizing the approaches to measure the magnitude of the informal sector, we firstly clarify the reasons, why we devote ourselves to measure the magnitude of the informal sector. Then we divide all the measurement approaches into three categories: the direct approaches, the indirect approaches, including five indicator approaches, and the MIMIC approach. In the study of each approach, we describe the approaches, show the application of the approaches, summarize the merits and limitation of the approaches and discuss the relationship between the assumptions and the disadvantages of the approaches. Finally, we compare the approaches from several aspects.