Omitted downstream attributes and the benefits of nutrient reductions: Implications for choice experiments

Discrete choice experiments have been used extensively to value environmental quality; however, some important attributes are often omitted due to design challenges. In the case of quantifying the values of water quality improvement programs that bring transboundary impacts, existing studies predominantly focus solely on local benefits. Using a statewide survey of Iowa residents, we provide one of the first estimates of willingness-topay for both local and downstream water quality improvements-Gulf of Mexico hypoxic zone reductionstemming from nutrient reductions. Using a split-sample design, we find that excluding hypoxic zone reduction as an attribute significantly reduces the total economic value of nutrient reduction programs. Moreover, we find evidence showing that such exclusion, in line with the theoretical prediction, only changes the preferences of respondents who are aware of the transboundary impacts of nutrient reductions. Conversely, our results also show that providing information about the downstream water quality benefits of nutrient reductions increases support for water quality improvement plans among local residents who are unaware of the connection between local and downstream water quality.