#Influencer marketing : The effects of influencer type, brand familiarity, and sponsorship disclosure on purchase intention and brand trust on Instagram

A relatively new approach for organizations to reach their potential consumers is by using in-fluencer marketing. The concept of a brand using celebrities as influencers to endorse their product is an established practice, however, influencer marketing has introduced a new ten-dency for using micro-celebrities as a new type of influencer. Additionally, an important part of the influencer’s social media message is the brand and also the fact that the message is spon-sored. The practical relevance of the field of influencer marketing is growing more and more, however, the previous research is inconclusive about which type of influencer in combination with what kind of brand and sponsorship disclosure will be most effective to use in social media. This is why the purpose of this study consists in determining the effects of influencer type, brand familiarity, and sponsorship disclosure on the purchase intention and brand trust of an individual. Furthermore, part of the research is to determine if attractiveness, trustworthiness, and expertise mediate the effect of the independent variables influencer type and sponsorship disclosure on the dependent variables purchase intention and brand trust. This research uses a 2 (traditional vs. micro-celebrity) x 2 (familiar vs. unfamiliar brand) x 2 (sponsorship disclosure vs. no sponsorship disclosure) factorial design in the form of an online experiment conducted only amongst Bulgarians using Instagram as the social media platform for the research. The most important results of the study are that micro-celebrities are more effective influencers compared to traditional celebrities as well as that the combination of a micro-celebrity with a familiar brand on the one hand and no sponsorship disclosure, on the other hand, proved to be more influential compared to these combinations with a traditional celebrity. Another important finding is that the mediating variables trustworthiness and expertise improve the effect of the micro-celebrity on purchase intention and brand trust. These results make an important contri-bution to advancing previous research on micro-celebrities and building the foundation for fu-ture research on micro-celebrities in combination with different types of products, as for in-stance – low and high involvement products. Future research can also measure existing attitudes towards the brand that the micro-celebrity is endorsing before and after the social media mes-sage in order to determine what role the brand attitude plays. In addition, using micro-celebrities in the practice can lead to more effective measures for increasing purchase intention of the audience and selecting an influencer based on their personal characteristics will lead to a suc-cessful influencer marketing strategy.