Besides some other criteria such as gender, age and geographical distribution, socio-economic status is one of the variables that determines whether or not the random sample chosen, upon which to conduct research, is representative of the population.

However, in Turkey and in the world, there is no single method of socio-economic classification that is agreed upon. In Turkey, the classification problem is a result of the fact that in population counts, there is no specific question related to income.

The socio-economic status is a composite variable constructed from several sub-variables. Efforts of the Turkish Market and Public Research Institute have helped related parties to come to an agreement on a classification methodology to some extent. Accordingly, the occupation of the main income earner, his/her education level and income are main composites in determining social grade. Since income cannot be easily identified and because it is not a sufficient determinant of socio-economic status, it cannot be used directly for classification. In addition to the occupation and education of the main income earner; his/her age, total years spent for education, his/her ownership level of consumer durables and domestic animals, the state of the house (flat, private house, toilet etc.) are some sub-variables that can be used directly or indirectly. However, it is not always possible to make a one to one classification mainly because of problems related with the classification of informal sector activities, rapid urbanization and the existence of middle social grades. Moreover, in the field research, it is not very practical to use a classification system based upon a complex and multi-variant calculation.