You know the feeling. You took the car to the mechanic, they said they fixed that odd knocking noise, then said a lot of incomprehensible things and took a load of money. But, as you drive away, there’s that nagging feeling: did they really do what they said? The knocking noise is gone but should it really have cost all that?
People have this feeling because they have just purchased a credence good – something with qualities that cannot be observed by the consumer after purchase, making it difficult to assess its utility.