| Social media is an interactive platform (e.g., Facebook and Twitter), where firms can share information about their brand and products, and where customers can communicate and share content with people within their network (Rapp et al. 2013). Social media has not only changed the way businesses attract and retain customers, but it has also allowed customers to interact with each other and with the firm. With the advent of social media, media fragmentation has made customers less prone to making decisions based on classic purchase funnel but rather they are more likely to make purchase decisions based on their own opinions, motivated by information from social media rather than from firm initiated marketing (Evans 2010). According to a survey from marketers, the main benefits of social media are the increase in exposure (brand awareness) and increase in the traffic (Colwyn 2014). Since customers are spending more of their free time on the internet and social media, marketers focus their marketing budgets towards digital advertising and social media (eMarketer 2014). Despite the increasing interest in social media, its effectiveness on brand sales is still unknown and unpredictable. Some marketers report increase in sales after using social media, while some report no realized growth in sales (Colwyn 2014). The correct use of social media can dramatically improve the firm’s performance through creating value and engaging with the customers; however, negative feeds can tarnish the brand’s image and sales (Trainor 2012). Due to social media’s rapid dissemination of information and a large number of customers engaged in discussion, the effect of social media on brand sales can change in a shorter period than the traditional marketing does. Understanding how the effectiveness of social media on sales changes over time in shorter time intervals (e.g., monthly or weekly) is important for marketers in order to promptly react to undesirable outcomes, and to frequently make resource allocation decisions, that can enhance the overall firm performance. The level of customer engagement and interaction among customers on social media can vary over time as changes in product life cycle (PLC) or business performance occur. Not only can customers engage with the brand (e.g., likes on Facebook or share posts), but they can also disengage with the brand (e.g., post negative comments) during the PLC (Srinivasan et al. 2015). Especially the power of microblogging (mWOM) to spread information rapidly can change the effectiveness of social media over time (Hennig-Thurau et al. 2015). The timevarying effectiveness of marketing on firm’s performance implies that a specific marketing effort (e.g., television advertising) can have a varying positive and/or negative impact on brand sales over time, depending on external factors such as competition and/or economy (Osinga et al. 2010; Stremersch and Lemmens 2009). Applying this idea of varying marketing effects over time, we aim to investigate the time-varying effectiveness of social media on brand sales for short-term resource allocation decisions (Raman et al. 2012; Saboo et al. 2016). |