The reply creation ration consists of two underlying metrics: the (1) first reply created ratio and the (2) last reply created ratio. They consider whether a user has made the either the first or the last reply in a comment-chain. These metrics indicate the tendency of the users to participate in discussions and are presented in one section. Hacker et al. (2015) and Viol et al. (2016) propose the metrics, which can be calculated on an ego-centric scope.

The calculation schema for the first reply ratio $fr$ and the last reply ratio $lr$ are similar. The mean is used instead of the median, as most users have a value of zero or one and no outliers are expected.

(1): 1. select all posts from a user
2. foreach post:
2b. check if it is the first reply
3. divide the count of first replies by count of all replies:
fr := first replies / all replies
(2): 1. select all posts from a user
2. foreach post: