If the methodology is asking people a happy German might say: "I can't complain", while a (hypothetical) unhappy person from elsewhere might declare everything

If the methodology is asking people a happy German might say: "I can't complain", while a (hypothetical) unhappy person from elsewhere might declare everything to be "totally awesome". If you ask people, these differences matter, unless instead of happieness you are instead interested in who uses which words to describe their situation.