## 2 Literature Review
### Theoretical Gaps and Research Questions  
We are interested in the impact of digital literacy on social platform adoption among the elderly and the effectiveness of platform promotional strategies. These studies on innovation diffusion have enhanced our understanding of social platform adoption; the  
Figure 1: Classification of the elderly. agent-based model developed in innovation diffusion research is very informative as a reference. However, two aspects need to be considered carefully while drawing on innovation diffusion research to model aged social platform adoption. First, the agent-based models derived from the innovation diffusion literature fail to carefully consider the various strategies that platform managers adopt to encourage customer adoption and participation of the platform. By reviewing the literature on social platforms, the main strategies of platform promotion address three aspects: strategies related to customers' hedonic value and relationship management (i.e., ensuring service quality and times of interactions), strategies directly related to information diffusion (i.e., increasing the strength of mass media messages, increasing the number of seeds) and strategies that encourage members to expand their influences (i.e., cultivating opinion leaders) [7; 27; 28]. Most campaign managers for general new products and services only use strategies that are directly related to information diffusion [39] and service quality [19; 24; 25; 26] because consumers can hardly interact with others as social platform users and have fewer chances to develop into an opinion leader and exert their influences within or outside the social platform. Additionally, previous literature did not mention individuals' differences in information activities due to their digital literacy in multistage platform adoption and their different behavioral responses to these strategies given their differences in digital literacy. As indicated in Table 1, previous innovation diffusion research has focused on groups such as social network users, game platform users, and cellphone consumers, but studies that focus exclusively on the elderly are rare. The existing innovation diffusion literature focuses on user characteristics such as interaction influences, demographics, and innovativeness--but not on digital literacy (see Table 1). We assume that the effect of promotion strategies is closely related to individual information seeking activities and the information sources they utilize. For example, the effect of mass media messages is related to individuals' information seeking capabilities [18]. The evaluation of service quality involves information seeking activities and the follow-up information processing process [41]. How and the probability that individuals become opinion leaders are also closely related to their information sources [19]. Considering the huge differences between PIRs and AISs in information seeking, information sources and information processing, the effect of promotional strategies on the target population with different proportions of PIRs and AISs may be different. Given the aforementioned two reasons, the rules of individual state transition and interaction between individuals in the process of platform adoption are different from those in general innovation diffusion processes. The corresponding agent-based model to describe the aggregated multistage individual behaviors and the interactions between individuals across the adoption process of elderly platforms should also be redesigned. Therefore, it is necessary to reconstruct the previous agent-based models to study the impact of the multistage behaviors of the elderly with different digital literacy on the macro results of platform adoption and how the effect of multiple strategies on platform adoption varies with different proportions of PIRs and AISs.