Twitter Rekognition Index (R-Index), inspired by the academic h-index, is a user-level metric that attempts to measure the impact of a Twitter user.
R-Index is a score between 0 - 100, calculated according to the retweet counts of the last 100 tweets of a user. An r-index of 30, for example, means that among the last 100 tweets of that user, 30 of them have been retweeted at least 30 times.
http://rekognize.io/r-index/api/r_index?screen_name=jack
{ "screen_name": "jack", "r_index": 84, "percentage": 1.7 }
Below is the live distribution of the Twitter users' r-index scores.