One area that often causes difficulty is the classification of demographic data. Many countries subscribe to a social-grade classification system, which uses a grouping system described as A, B, etc. There the similarity often ends, with the number of groups and their definitions differing widely. The UK has a six-grade system (A, B, C1, C2, D, E), Ireland a seven-grade system (A, B, C1, C2, D, E, F) and India an eight-grade system (A1, A2, B1, B2, C, D, E1, E2). Many developing countries have no commonly acknowledged system of social-grade classification, and local researchers may all have their own approach. Level of education may be used as a surrogate for social grading or to complement it, but education systems similarly vary between countries. Terminal education age is something that can be measured in a consistent way between countries, but its implications are likely to be very different.
Alternatively, a measurement of living standards can be obtained by asking about ownership of durables. That too must be tailored to the local situation. Ownership of a moped, fridge or television might indicate a very different level of social grade in, say, Vietnam and Germany.
Source: Brace Ian (2018), Questionnaire Design: How to Plan, Structure and Write Survey Material for Effective Market Research, Kogan Page; 4th edition.