Sector studies are a tool that the IRS uses to detect the fundamental parameters of professionals, self-employed and businesses.
The main part consists of the systematic collection of data that characterize the activity and the economic environment in which the company operates, in order to evaluate its ability to produce real income and are used for determining induction of artists and professionals and businesses.
The introduction of sector studies in Italy began August 30, 1993  and has annually enriched with new tables on the vast majority of business sectors. To allow taxpayers and tax advisors to manage the diversity and complexity of the information required for each type of field study, every year is making available a software process, called Jericho.
There are many analyzes on the various options relating to the application, adaptation and to investigations arising from field studies , as well as disputes and litigation resulting from their application. 
Sector studies are divided into four main areas:
• Services (SG, TG, UG)
• Commerce (SM, TM, UM)
• Manufactures (TD, UD)
• Professionals (SK, TK, UK)
Each set of tables is indicated by a code of five characters that allows you to connect each code of economic activities (NACE 2007) to the study of the Internet industry.  The first two characters are the ones listed above, the first provides an indication of "temporal" the study of the field, the second identifies the macro reference.
2. Development of sector studies
Sector studies are constructed according to a rigorous statistical procedure that is reviewed and approved prior to their entry into force, the so-called Commission of Experts, a body made up of representatives of the Inland Revenue and the Ministry of Economy and organizations.
The procedure is essentially in these phases: collection of quantitative and qualitative elements of an activity, identification of a consistent method for carrying out the same (cluster) determining revenues alleged activity.
The first phase of data collection takes place on the occasion of the introduction of a new industry study or update an existing study. Taxpayers are sent to special questionnaires requesting information on its activities, both organizational accounting practices. If there is already a study of the industry, are also used in updating the data transmitted by the taxpayers in completing the study. It is expected the standard deviation of the data relating to activities absolutely abnormal, which may affect the reliability of the sample.
The second step is to identify within the study area for a given activity, methods of undertaking the same as homogeneous as possible between them. The examination of the data collected is done through a statistical technique called principal component analysis, allowing you to identify the most important variables for the formation of clusters. It is then applied to cluster analysis, allowing a homogeneous models of carrying out the activities. For example, the study area for the bar identifies 18 clusters.
The third step is to determine a function of estimated revenues alleged. This function within each study is different for each cluster. It uses a statistical technique called multiple regression, whereby posed as independent variables the structural data and accounting activity as the dependent variable and the revenues, it is possible to determine the function that estimates the latter with a degree of error negligible.
3. Outcome of the application of the study area
After completing the model of the study area, the application Jericho immediately provides the results of the calculation with respect to:
• reference cluster
• economic consistency
• economic normality
3. 1. Reference cluster
Through further statistical technique called discriminant analysis, each taxpayer is assigned to the cluster, the more similar to their own situation. The outcome of the analysis is seen in terms of probability: Jericho gives the probability that a taxpayer falls in a certain cluster. Frequently, it may be that a taxpayer has a probability to belong to multiple clusters (for example 30% of belonging to the cluster 1 and 70% of belonging to cluster 7). In such circumstances, the subsequent analyzes are weighted based on the probability of belonging.
3. 2. Economic consistency
The analysis of the economic consistency compares the value of some indices, calculated on data reported by the taxpayer, consistent with values considered for the cluster considered. For example for the index of coherence reloading is provided a minimum and maximum value. Taxpayers who are placed in the range are considered to be consistent. The positions that are inconsistent can be used by offices for the selection of taxpayers to be subjected to any controls.
3. 3. Adequacy
The suitability analysis aims at estimating a revenue alleged, resulting from the application of the regression function to the variables indicated by the taxpayer. Since this is a statistical calculation indicates Jericho:
• the proceeds timely, considered as the most probable value estimated;
• the confidence interval, which is a minimum value (referred to as the minimum return) and maximum (which is not shown), whose average income is punctual. It is considered likely that 99.99% of the proceeds of the subject considered to be within the confidence interval.
The taxpayer must compare its revenue with those allegations, considering:
• reasonable, if the revenues are higher than stated on time;
• not appropriate, if the revenues are less than accurate. In this case, it may be inspected and the office could not stating contestargli revenues "missing" to get to the point. The taxpayer can evaluate to adapt spontaneously declaring the difference (however, be an increase of 3% on the adjustment made).
Note that the taxpayer is not appropriate, you may have sales that are higher than the minimum return and therefore fall within the confidence intervals. In this case, while precluding the possibility of control, financial offices has been suggested to focus on other positions, given the high probability of reliability of reported revenue.
3. 4. Economic normality
The analysis of economic normality, experimentally introduced from the year 2006 and then a final, aims to identify some indicators (so-called INE, indicators of economic normality), whose outliers may suggest an activity carried out in "non- normal "or to incorrect compilation of the study area. Similarly to the indicators of consistency, for each cluster are defined a minimum and maximum value of each INE, provided by the studio. According to the indications of each technical note of the study of the field, an index value above the maximum or below the minimum (a second, not necessarily both) is to consider not normal compared to the cluster considered. The situation of normality is not resolved, since each INE provides, on the basis of a specific formula, that in case of non-normality, are alleged higher revenues than those of congruity, estimated by the regression function. For example, suppose that the incidence of the cost of capital goods on their value is considered normal up to 0.20. If the calculated value is 0.30, this means that the taxpayer incurs costs to assets above the norm and, consequently, it is assumed that he obtain higher revenues. Revenues are presumed to be based on the INE (note that there may be multiple INE abnormal and each gives a higher income), must be added to the revenue on time.
For field studies involving INE "definitive", the taxpayer must declare to be sufficient revenues: revenue + punctual revenues alleged by INE. For the 2006 tax year and for studies that still maintain the INE "experimental" is considered a reasonable income higher than the higher of:
• Revenue on time, without taking into account the INE;
• minimum revenue increased revenues resulting from the INE.
2. Industry studies: how to neutralize the deviations from the indices, by Il Sole 24 Ore
4. Bridging table field studies and Ateco 2007
5. Related items
• Revenue Agency
6. External links
• The section on field studies at the site of the Revenue
• Jericho Software for the management of revenues from the sector studies and for the preparation of electronic files to attach to UNICO 2010
Translated via software
Italian version of ReteIngegneri.it