In recent years in the specialized sectors of B.V.A., I have been confronted with a complex problem common to diverse specific economic sectors. The major aim of the solutions sought was to provide advertisers responsible for advertising budgets very much smaller than the budgets of the general public, with reliable tools for measuring usage, audience, or choice of advertising at the cheapest cost possible, of course - and they had to be tools that could could reach unusual targets. Our research was therefore based on two concerns which may appear controversial at first sight: - The offer of tools with high reliability, thus enabling the study of very specific populations, which are difficult and sometimes impossible to reach with classical tools. - The offer of very competitive prices feasible for limited budgets. The following remarks are illustrated with several examples drawn from surveys carried out by our institute - first of all, in the field of agriculture, where the problem has been solved for several years. Secondly we launched surveys In the following areas: construction prescribers, cafes, hotels, restaurants (CHR), chemists, transport companies, amongst others.