The thread creation ratio is a pair of two underlying metrics. The (1) ratio between the number of threads and the total posts and (2) the ratio between initiated threads and total threads in the network.
Smith et al. (2009) call these two metrics Verbosity and Initation, while Angeletou et al. (2011) are writing about Thread Initation Ratios. These metrics were later picked up by Hacker et al. (2015) and Viol et al. (2016). They are of ego-centric scope as they can be calculated for individuals, although the calculation of an average over the whole network is feasible.
The calculation of the single thread creation ratio $st$ and the total thread creation ratio $tt$ is straightforward and can be accomplished in one step each:
(1): st := select count of threads / count of posts (2): tt := select count of initiated threads / count of all threads
Viol et al. (2016) and Hacker et al. (2015) conclude that a high number of threads compared to the number of posts, is a sign of information sharing. A user with many threads is informing other users about events or other news. However, Hacker mentions that their analysis result does not support this notion for threads, which do not receive any replies. These may be unanswered questions or uninteresting posts.
Another notion presented by Viol et al. (2016) is that a high value indicates users who share knowledge and ideas with others, spawning new discussions threads. These discussion threads contribute content and ideas to the network. This fits with the first interpretation that replies are needed in the threads.
Hansen et al. (2010) describe such users as discussion starters and Rowe et al. (2013) as expert participants, while Angeletou et al. (2011) speak of popular initators. Due to their creation of threads, they are usually well known in the network and have high visibility. Users with a low ratio only post occasionally and are unlikely to start their own topics. Smith et al. (2009) claim that more threads are better for the network as it indicates the generation of new ideas and discussions.
Social relationships are only formed, when other users respond to a thread. Therefore this metric alone is not sufficient to make any claims about Social Capital. However, if a particular thread gathers attention, this indicates a high level of engagement in discussions and the exchange of new ideas. This facilitates Bonding Social Capital as people exchange their thoughts and ideas to form a shared understanding.