Is it true that almost everyone who starts a PhD and sticks around long enough can get one? Not referring to degree mills here, but genuine PhDs.

This claim comes from this blog post by Cardiff University psychologist and neuroscientist Chris Chambers:


  A PhD is essentially a test. Don't fool yourself into thinking that you pass this test by passing your PhD. Wrong. The fact is that passing a PhD is like getting a certificate of participation. Why? Because almost everyone who starts a PhD and sticks around long enough ends up getting one. No, the real test is what happens after your PhD. That's when you’ll know whether you’ve really passed. Do well and it will open the door to a career of unparalleled intellectual freedom.


(emphasis mine)

The claim sounds fantastic to me. Is it true? Are there any statistics that indicate it to be so? Chris Chamber's post links to a source, but unfortunately it appears to no longer be available.
From what I have seen, this is pretty much the case for PhD programs in Europe. PhD programs in Europe tend to work a bit differently than in the US. It is typically expected that you have already completed a Master's degree before starting a PhD. The PhD program itself tends to have little or no coursework requirements, and no examinations other than the thesis defense at the end.

A lot of filtering that is done in US programs through exams during the program, is instead done at the selection stage. Consequently, landing a PhD position in Europe can be more difficult than in the US. But once you got the position, it is very rare for people not to get their PhD in the end. People on occasion may drop out of the program. Much more rarely, a program may decide to drop a candidate if things are really not working out. If that happens, it typical happens in the first year. But overall in the various locations I have been, at least 80% of people who start PhDs in Europe end up with a PhD.  

Some actual data:


According to this article in the Times Higher Education, PhD completions rates in the UK are about 73% after 7 years, grow up to just over 80% eventually.
This post by the Dutch association of Universities shows similar numbers.