There exists a large literature that analyzes the impact of expert opinion on consumer choice and demand for experience goods. Due to the non-experimental nature of most prior studies, endogeneity is a concern. Specifically, there is likely a spurious correlation between good reviews and high product demand that exists because of an underlying correlation with unobservable quality signals. This paper avoids such obstacles through an experiment approach.

Specifically, this study examines the impact of expert opinion on retail wine purchases. Anecdotal evidence suggests that consumers are largely uninformed regarding the quality of wine products: thus, wine is an experience good. There exist many sources of expert opinion for wine, including Wine Spectator and the Wine Advocate, which have reviews for more than 300,000 wines. However, little is known regarding the impact of such expert reviews.

To examine the impact of expert opinion, we utilize an experimental approach at a large national retail grocery chain. In particular, wines in two retail stores in Northern California were randomly chosen to display wine scores from the Wine Spectator and Wine Advocate. Wine opinion labels were displayed for one month during Spring 2006 for 200 wines. Wine sales in the treated stores were then compared to sales of these wines in stores that displayed similar trends in wine sales both before and after the
treatment period.

We find that while demand decreases for wines that receive low scores, demand for average- and higher-than-average-scored wines increases. The results indicate that expert opinion labels transmit quality information that affects demand as opposed to solely increasing the wine's shelf visibility to the consumer.

These results have important implications for understanding how to effectively market wine and other consumer products reach and influence consumer behavior. Specifically, our results demonstrate that expert opinion labels can substantially increase wine sales. More broadly, for products where consumers' product knowledge is incomplete, the display of quality information may induce consumers to enter the market or to purchase such products on a more regular basis.

This study examines the relationships between water quality and socio-economic-demographic factors in California at the county level using 24 water quality indicators coming from seven different types of bodies of water. It estimates three classes of models: the traditional per capita income-pollution level specifications (the environmental Kuznets curve, EKC), a more inclusive model containing main socio-economic-demographic variables, and a model that includes these variables while accounting for spatial correlations too. For most water quality indicators, it does not find support for income-pollution specifications. For pollutants like phosphorous and total suspended solids, the level of agricultural activity is a significant determinant of water quality in California. However, for other surface water pollutants commonly considered agricultural pollutants, such as ammonia and nitrate, the level of agricultural activity is not statistically significant. Additionally, education, ethnic composition, age structure, and water area are all significantly correlated with various
indicators of water quality.