Willingness to accept (WTA) is usually higher than willingness to pay (WTP) for different types of goods. Studies over 30 years show that the less a good is like a regular market item, the higher the WTA/WTP ratio. Non-market goods have the highest ratio, followed by private goods, and then money-related experiments. Even when survey design differences are considered, ordinary goods have lower ratios than non-ordinary ones. Real and hypothetical experiments show similar ratios, and incentive-compatible methods result in higher ratios.