What is contingent valuation as it relates to alternative methods for estimating the value of environmental regulations?

• Linking the amount of pollution to healthcare costs to estimate the cost of regulation
• Using the change in property values in response to a change in pollution to provide an estimate of the cost of pollution
• Comparing how much it costs to clean waste sites to the cost of regulation
• Multiplying the amount of people who are willing to pay for trips to natural resources by the number of citizens to construct an estimate on the value of environmental goods