The phenomenon of the informal economy is one of the old economic phenomena, and it have known in all economies, developed and developing countries alike, however the interest in this phenomenon has not only started since the seventies of the last century. In spite of the agreement the majority of economists on the existence of the phenomenon of the informal economy, but they differ in their definition and appreciation of the magnitude of the phenomenon and analysis of the causes and consequences.
And that failure to record the activities of the informal economy (the legal aspect) and of next to (the irregular economy), and control (the non-legal and illegal) activities of the informal economy and of the side (black economy) or (the crime)
Lead to negative effects associated with lack of accuracy of data and poor knowledge of the movement of the economic system in its various sessions such as ,the production cycle ,the expenditure cycle ,income distribution cycle ….etc . And inaccurate assessment of the performance of the national economy and a high degree of uncertainty surrounding the true size of the aggregated key .
This research aims to put a definition to phenomenon of the informal economy and shows the activities by both sides ,the legal and illegal ,and knowing the economic and social affects that result from this activities on the national economy ,and the ways to deals with this activities all by its type ,and shows the size in the world nation as percentage from GNP for the duration from( 1999-2000/2004-2005) and what the ways that estimating this phenomenon .
The research attempted to measure the size of the phenomenon of the informal economy in Iraq for the duration of the (1976-2005), through the analysis of some indicators of the Iraqi economy for the duration(1970-2005). And knowledge of the most important imbalances faced by the Iraqi economy, and then indicate the results of measuring the size of the informal economy and attributed to the gross domestic product in the Iraqi economy. And analysis of those results, and then exit the conclusions and the formulation of relevant recommendations.