Number of citations after PhD I am trying to compare PhD training programs of different universities, institutes and departments in my field of interest. One of the comparisons I made is where did the previous students go after they finished their PhDs; how many papers did they write during their PhDs; and how much are they cited 1-2 years after completing their PhDs.

Now, comparing the citations counts is difficult. They vary quite a bit. How many times should  a successful young scientist be cited 1-2 years after completing his or her PhD? How about an average one? What is the minimum number to be able to continue in academia? I understand that exact numbers are difficult to provide but I would guess you senior scientists can provide good estimates.
Although this approach to measuring is plausible, I fear it is not what you want. Although of course things vary by field, the papercount per se, or even "impact factor", or ... any other easily-measurable thing is not quite what will affect things.

At least in mathematics (my field), a smaller number of very-good papers is much better than a large number of irrelevant papers. One might imagine that this would be measured by "impact factor", but it is absolutely not reliably so. As an extreme case, consider what happens when an important problem is finally and definitively solved: there may be fewer follow-ups, fewer citations, simply because there's little more to say.

And there's time-lag: I have many examples of 10-20 year (and longer) delays before people widely realized the interest of a given paper. Srsly, surely we're not trying so much to be of-the-moment-celebrities, but to make a long-term impact. 

One could go on-and-on about the unreliability of appealing-but-fatally-flawed metrics... but the real point is that a less objectifiable judgement is necessary to evaluate the "merits" of a program. Stats on the students is probably not quite what you'd want, even though it might seem to be. E.g., at more elite places, there is vastly greater variance among students... so the "outcomes" are harder to interpret meaningfully... and, for you yourself, what those other kids did or didn't do is operationally irrelevant:

That is, your level-of-performance, that causes (or doesn't) respected experts to commend you to their peers, is what will get you a job, or not. The "published papers" thing is a side-effect.