Any data for average number of papers per year at different career stages?
Italy introduced a few years ago a habilitation process which involves heavy bibliometric evaluation, and in the process they computed median values for all the professors in Italian universities for:

number of papers published in 10 years
citations per year
a sort of normalized H-index: the number h such that the person has h papers with score &gt;=h, where a paper published Y years ago with C citations has score 4C/Y. (more precisely defined here (Italian) and here).

The medians are separate by discipline and academic role (associate and full professor only --- not for assistants, unfortunately). You can find them here: associate full, and a legend for the codes of the scientific disciplines is here. The documents are in Italian, but you can google-translate them (or guess the meaning of most words, it's not too difficult for an English speaker).
For instance, in computer science (01/B1) the medians for an associate professor are

10 journal papers / 10 years,
9.15 citations / year
&quot;contemporary H-index&quot; 5.

and for a full professor

12 papers / 10 years
14.8 citations / year
&quot;contemporary H-index&quot; 6.

The calculations are of course imperfect, but they are very interesting to browse and give an idea of how wildly these numbers vary across different fields. For instance, the typical professor in nuclear physics (02/A1) publishes 59.5 papers over 10 years and gets over 104 citations per year, while one in mathematical logic (01/A1) publishes 5 papers in 10 years and gets 1.74 citations per year.