Establishing predictive validity of measures is a major concern in marketing research. This paper investigates the conditions favoring the use of single items versus multi-item scales in terms of predictive validity. A series of complementary studies reveals that the predictive validity of single items varies considerably across different (concrete) constructs and stimuli objects. In an attempt to explain the observed instability, a comprehensive simulation study is conducted aimed at identifying the influence of different factors on the predictive validity of single versus multiitem measures. These include the average inter-item correlations in the predictor and criterion constructs, the number of items measuring these constructs, as well as the correlation patterns of multiple and single items between the predictor and criterion constructs. The simulation results show that, under most conditions typically encountered in practical applications, multi-item scales clearly outperform single items in terms of predictive validity. Only under very specific conditions do single items perform equally well as multi-item scales. Therefore, the use of single-item measures in empirical research should be approached with caution, and the use of such measures should be limited to special circumstances.

The traditional new product development (NPD) model, in which companies are exclusively responsible for coming up with new product ideas and for deciding which products should ultimately be marketed, is increasingly being challenged by innovation management academics and practitioners alike. In particular, many have advocated the idea of democratizing innovation by empowering customers to take a much more active stake in corporate NPD. This has become feasible because the Internet now allows companies to build strong online communities through which they can listen to and integrate thousands of customers from all over the world. Extant research has provided strong arguments that indicate that customer empowerment in NPD enables firms to develop better products and at the same time to reduce costs and risks if customers in a given domain are willing and able to deliver valuable input. Customer empowerment, however, not only affects the firm's internal NPD processes as reflected in the products that are ultimately marketed. Instead, it might also affect the way companies are perceived in the marketplace (by customers who observe that companies foster customer empowerment in NPD). This paper provides the first empirical study to explore how customers from the ''periphery'' (i.e., the mass that does not participate) perceive customer empowerment strategies. Customer empowerment in NPD is conceptualized along two basic dimensions: (1) customer empowerment to create (ideas for) new product designs; and (2) customer empowerment to select the product designs to be produced. Therefore, customers may be empowered to submit (ideas for) new products (empowerment to create) or (2) to ''vote'' on which products should ultimately be marketed (empowerment to select). In the course of two experimental studies using three different product categories (T-shirts, furniture, and bicycles) both customer empowerment dimensions (as well as its interaction) are found to lead to (1) increased levels of perceived customer orientation, (2) more favorable corporate attitudes, (3) and stronger behavioral intentions. These findings will be very useful to researchers and managers interested in understanding the enduring consequences of customer empowerment in NPD. Most importantly, the results suggest that empowerment strategies might be used to improve a firm's corporate associations as perceived by the broad mass of (potential) customers. In particular, marketers might foster customer empowerment as an effective means of enhancing perceived customer orientation. Customers will in turn provide rewards, as they will form more favorable corporate attitudes and will be more likely to choose the products of empowering as opposed to nonempowering companies, ceteris paribus. Customer empowerment thus constitutes a promising positioning strategy that managers can pursue to create a competitive advantage in the marketplace.

Companies have recently begun to use the Internet to integrate their customers more actively into various phases of the new product development process. One such strategy involves empowering customers to cooperate in selecting the product concepts to be marketed by the firm. In such scenarios, it is no longer the company but rather its customers who decide democratically which products should be produced. This article discusses the first set of empirical studies that highlight the important psychological consequences of this power shift. The results indicate that customers who are empowered to select the products to be marketed show stronger demand for the underlying products even though they are of identical quality in objective terms (and their subjective product evaluations are similar). This seemingly irrational finding can be observed because consumers develop a stronger feeling of psychological ownership of the products selected. The studies also identify two boundary conditions for this "empowerment-product demand" effect: It diminishes (1) if the outcome of the joint decision-making process does not reflect consumers' preferences and (2) if consumers do not believe that they have the relevant competence to make sound decisions.

The authors study consumer perceptions of firms that sell products designed by users. In contrast with the traditional design mode, in which professional designers employed by firms handle the design task, common design by users involves the firm's user community in creating new product designs for the broader consumer market. In the course of four studies, the authors find that common design by users does not decrease but actually enhances consumers' perceptions of a firm's innovation ability. This "innovation effect of user design" leads to positive outcomes with respect to purchase intentions, willingness to pay, and consumers' willingness to recommend the firm to others. The authors identify four defining characteristics of common design by users that underlie this innovation inference; namely, the number of consumers, the diversity of their background, the lack of company constraints, and the fact that consumer designers actually use the designed product all contribute in building positive perceptions. Finally, the authors identify consumer familiarity with user innovation and the design task's complexity as important moderators that create boundary conditions for the innovation effect of user design.