The purpose of this research is to measure how effective social influencers and celebrity endorsers are in persuading individuals to like, purchase and/or share information about a brand or specific product. Previous literature has discussed how different source characteristics and endorsers influence individuals. However, rapid change in information and communication channel evolution means that the research on endorsements conducted before social media channels arose is in need of updates and extensions to examine how current forms of communication drive brand conversations.
Source characteristics impact how a social influencer or celebrity endorser is effective when communicating to an audience. In the endorsement setting, the most important attributes are trustworthiness, expertise, attractiveness, authenticity and credibility (Erdogan, 1999). As the literature shows, these attributes are the most likely to contribute to attitude change and eventual behaviour change (Erdogan, 1999; Kapitan & Silvera, 2016). These attributes have been individually studied for celebrity endorsers (i.e., Erdogan, 1999), however, the rise of online social influencers makes it important to re-evaluate and compare and contrast social influencers and celebrity endorsers so that brands, endorsers and researchers have a better understanding of what viewers are looking for.
Two areas of interest drive the quantitative research undertaken in this thesis: (1) an evaluation between attitudes generated by social influencers and celebrity endorsers and (2) the willingness to purchase an endorsed product or brand depending on endorser type. Research question one asks if a social influencer has a different effect on consumers’ evaluations compared to a traditional celebrity endorser. In research question two, this thesis examines if consumers are more likely to purchase a product endorsed by a social influencer or a traditional celebrity endorser. The research questions will be answered using six hypotheses:

H1: Social influencers (vs. celebrity endorsers) encourage more positive attitudes towards the endorser.
H2: Social influencers (vs. celebrity endorsers) generate higher perceptions of authenticity in the endorsement process. H3: Social influencers (vs. celebrity endorsers) generate higher perceptions of trustworthiness in the endorsement process. H4: Social influencers (vs. celebrity endorsers) generate higher perceptions of expertise in the endorsement process. H5: Social influencers (vs. celebrity endorsers) encourage more attributions about the endorser liking, desiring, valuing and using endorsed products.
H6: Consumer attributions about an endorser liking, desiring, using, and valuing the products they endorse will mediate the effect of endorser type (social influencer vs. celebrity) on willingness to pay for the endorsed product.

Using online platform Qualtrics, a study was distributed through channels including Cint, LinkedIn, Facebook and Instagram, and 226 participants took part in the main study. The research rejects H1; however, fully supports H2, H3, H4, H5 and H6. Importantly, this indicates that when endorsing the same product category (i.e., beauty products or electronics as tested in this thesis), celebrities and social influencers are rated with equally positive attitudes. This null finding reveals that social influencers are an accepted group of endorsers. Findings further reveal that, throughout the endorsement process, individual consumers perceive social influencers to be higher in authenticity, trustworthiness and expertise than celebrity endorsers. Additionally, consumers are more willing to believe that social influencers actually like, use and desire the product they endorse, which mediates purchase intentions.