It's working exactly as intended. You need a VPN to access certain websites, some keywords are censored properly. How is that an example of not working?
Police forces are unable to prevent people from committing crimes.
True - But police forces are phenomenally capable at both stopping a lot of people from committing crimes, and dissuading people from even thinking about committing crimes.
They also raise the barrier of entry (so to speak) for being criminal.
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In today's day and age, a great firewall will work. The average person does NOT have the patience or inclination to go figure out a VPN. Heck I couldn't be arsed, and I am dramatically more capable than the average person.
But there's an additional risk you should consider.
Great firewalls are content to let the minority get away with accessing other sites, as long as they don't make themselves a nuisance.
Instead, they train the Average person, and the average populace to behave in a particular manner.
And that shift means that future generations of tinkerers, thinkers are the ones which will start out far removed from a natural set of ideas.
You can't cheat everyone all the time. The point is not cutting China out from the Internet, but keep sensitive information in the educated elites, not the masses.
As a bonus, they created parallel version of services that exist on this side of the firewall.
Well it prevents 99% of the people who don't know how or don't bother setting up VPN from accessing prohibited content, that's the intended effect. So I would say it's working well.
And that's just people who explicitly use it. With that kind of market penetration basically everyone knows what to do, or who to ask if they want to access some geoblocked service in the future.
According to my observations now here in China, your stats are wrong.
Edit: Just to substantiate, many people I spoke to vaguely know what they would see if they get unfiltered internet, so there's not really much motivation to bypass GFW.
Sorry, but this is an anecdote. Do you have a source that shows some usage? I'd love to see that, whichever side it agrees with, but personal experiences rarely generalises to nations.
Interestingly with censorship being such a sensitive topic in China, it's hard to find statistics on VPN usage rate. I will just say that I'm a Chinese citizen who visits China regularly every year. My impressions can't be too far off from the actual stats.
On the other hand, it blocks 0% of people who have the intent to access that content so it doesn't really work at all for the people it's supposed to stop.