Percentage of PhD's in mathematics with no publications I have recently read the following statistics in the book "The Survival of a Mathematician: From Tenure to Emeritus" by Steven G. Krantz, which seems a little odd:


  It is a hard fact that more than 90% of American Ph.D. mathematicians
  never write a paper. Of those who do, most write just one paper based
  on the Ph.D. thesis and that’s it. Nothing more.


I have seen several new PhD's (graduated in Canada, US, or Europe) with no publications, but my estimate for the rate of such fellows was way more optimistic than the above quote. So, I would like to know: 

How accurate is this statistic? Is it documented anywhere?

Are there similar statistics about Mathematics PhD's in other countries?
I sent an email to Professor Krantz mentioning the present discussion and asking him whether his numbers are "supported by published or rigorously gathered data, or your own observations, or are simply meant rhetorically".  Here is his response, posted here with his permission.  

Summary: he does not appear to have data at hand to support those numbers, but he believes they are accurate.


  Dear Nate,
  
  Your question is a good one.  
  
  Certainly my statement is well supported by my own personal
  observation---after forty years in the business.  But I have seen
  sources even recently that say pretty much the same thing.  I'm sorry
  that I can't say what those sources are.
  
  You can think about the matter this way.  The vast majority of
  academic jobs in this country are at what we call comprehensive
  schools.  And those are places where teaching is the thing.
  Generally speaking, people don't do much research there.  They have to
  publish a paper or two to get tenure, and those papers tend to be
  fairly close to the thesis.  But then that's about it.
  
  A lot of other people get jobs at the National Security Agency, or Los
  Alamos, or another government think tank.  Generally speaking,
  publishing is not the thing there either.  Sometimes people publish in
  special classfied government journals.
  
  Other people get jobs at Microsoft or Hewlett-Packard or what have
  you.  And publishing is not the thing there either.
  
  Those of us who are lucky enough to be in math departments at true
  research universities are definitely in the small minority.
  
  I believe that, at the time I wrote those words, I consulted some
  people at the American Mathematical Society and they had data to
  support what I was saying.
  
  Feel free to quote me to others if you wish.
  
  Best,
  
  Steve Krantz