yes. you don't want to bore your examiners. and secondly some universities have a certain word limit (mine has page limit too). So you need to be conscious about what you want to put in.
depending on your research topic. Are you talking about measuring efficiency of financial system or the effectiveness of the measure (x-efficiency, productivity of the financial sector)
If it is just a thesis on banking - then I don't think you need to get too detail with the definition. but if you are trying to come up with a measure, or using different measures. Then you may have to look at different definition of concentration of commercial banks.