Social proof is ineffective at spurring costly pro-environmental household investments

One of the most popular techniques of persuasion in online marketing is social proof, also referred to as social validation. It takes advantage of the fact that when other individuals have decided in favor of a particular behavior people are more likely to follow that behavior as it is perceived as more valid. Yet there is a theoretical reason to be skeptical about the effectiveness of this persuasion technique for the encouragement of more costly investment decisions taken under high uncertainty. This study investigated the effectiveness of social proof in influencing consumer responses to calls for action on a bank's sustainable home improvement website. A first field experiment investigated whether participants engaged more with a webpage that provided a personalized testimonial or informed users that thousands of other clients had used the bank's sustainable home improvement services. A second field experiment encouraged clients to use the bank's services to obtain solar panels and we again investigated whether clients engaged more with a webpage that provided a personalized testimonial rather than without such a testimonial. Clients were directed to these webpages through a newsletter that is distributed to half a million clients of the bank. Overall, our evidence suggests that messages of social proof are ineffective at urging customers to consider larger pro-environmental household investments, let alone making those investments.