The using here are originally obtained from 10% of world-wide tweeting within in every 15 minutes, private tweets not included. Basic filtering applied for acquiring our hashtag data by 1) eliminate retweet, 2) eliminate non-English speaking Twitter account (however, non-English tweets in certain circumstances are allowed), 3) eliminating tweets without hashtag. Upon above, tweet hashtags are extracted for every tweet based on Twitter’s official detection, and thus have the level-1 hashtag data.