In China, online censorship is something the population has to deal with on a daily basis. Post something the government deems unfit for public consumption, and it will be removed. Continue to post inappropriate content and your accounts, and even access may get shut off.But how quickly can the censors react to such content? Two computer scientists, Jed Crandall and Dan Wallach, took up the challenge of trying to answer that question by monitoring China’s popular Sina Weibo microblogging platform for 30 days last year. The results may surprise you.Sina Weibo, like every company running an online service in China, has to follow the rules and censor inappropriate content its users post. If it doesn’t, the company itself will be held to account. That’s tough to achieve when you have 400 million registered users and 100 million new messages every day. Crandall and Wallach monitored 3,500 of those accounts, and were able to figure out some interesting facts about how the Weibo censorship system works.First, and most obviously, the system must be heavily automated. If it wasn’t, they estimated Sina Weibo would need to employ at least 4,000 censors working full time and in shifts 24 hours a day. Weibo actually employs two keyword systems. The first is a list of words that stop a post going live in the first place, the second marks a post for further investigation, which can be done by a moderator.How quickly the censorship system reacts to new posts is pretty impressive. A post can be deleted within 8 minutes of going live. 30 percent of deletions happen in the first 30 minutes, and most (90 percent) are deleted within 24 hours. It gets worse for repeat offenders, though. Reposting the same content see an automatic deletion or moderated deletion within 5 minutes, and new posts from the same user are dealt with even more quickly, meaning offenders get placed on a priority censor list of some kind. It’s also not uncommon to see account bans for reposts and repeated posts that need censoring.During the 30 days of monitoring the researchers saw 12 percent of the 3,500 accounts they were monitoring banned. But they also saw signs of real people being involved in the process because censorship levels dropped noticeably at specific times of the day, for example, when the 7pm news is on.When you consider that over 42 percent of China’s billion-strong population is online, you can see how big of an operation censorship is for online services. Teams of people must be dedicated to implementing censorship systems and moderating a service in real-time. And with companies focused on making money, you can only see such systems being improved upon and becoming more automated in the future to save on costs. We’ve already seen this happening with Weibo delaying posts going live for up to 7 days, and China’s Great Firewall gaining the ability to learn and censor more effectively.