There have been many efforts to place an economic value on environmental goods, but no consensus yet exists on the method of valuation. The challenges in the way of obtaining these economic values include the
free-rider problem, difficulties in assigning ownership, and the non-divisibility of environmental goods. Small scale simulated markets have been used in conjunction with
contingent valuation methods in order to assess the relative values of economic goods, as well as an attempt to assign them dollar values. Other studies criticize these methods for expecting an unrealistic amount of mental effort on the part of the subjects who are asked to assign values, as well as for introducing
framing effects and inherent biases relating to subjects' perceptions of dollar values.
Measures of economic progress Alternative measures of economic progress, including the
Genuine Progress Indicator,
Gross National Happiness, and
Gross National Well-being factor living environmental wellness, ecological vitality, and the effects of
resource depletion and long-term environmental damage into their models. These metrics aim to categorize not only the economical and monetary values of environmental goods and services, but also their effects on the emotional and psychological well-being of individuals within a society. == Trade definition ==