Q:

What is the average number of articles written per author in a year and has it increased recently?

Did anyone research the data about scientific productivity? I.e. what is the average number of articles written by author in a year in a specific field? I am  referring to average, since this is maybe easiest to calculate, but it would be interesting to see the distribution data too. This of course depends on how many journals we want to scope, but I would be interested to see any data on say most popular fields like physics, mathematics, chemistry, biology, psychology, economics, etc (order is of no importance).

A:

A comprehensive review was conducted in the field of psychology in relation to publication rates and tenure. There is also a "fun" review related to beer consumption and publication in the field of avian evolutionary biology.

doi: 10.1111/j.1467-9280.2007.01889.x
Psychological Science April 2007 vol. 18 no. 4 283-286

A:

Though this is not a direct answer to your query, this hopes to lead to more productive / useful answers.
See this Wiki article, on Hirsch index or h-index that is a widely accepted measure of 

both the productivity and impact of the published work of a scientist
  or scholar.

The article also points to other indices on scientific/academic productivity and impact in the field.
The SAO/NASA Astrophysics Data System Abstract Service provides a gateway to the online Astronomy and Physics literature. A new interface of the ADS provides a tool to visualize the author and paper networks; that tells you how productive the author is, quantified with the number of collaborators and papers produced.
For e.g. see this link; a search for the name Narlikar. On top of the resulting page, next to Top 200 results, you can see a drop-down menu, on which you can select various options like Author Network, Paper Network etc to get various  visualizations.
You can contact the project personnels here http://adsabs.harvard.edu/ . They do conduct studies on bibliographic data, which is one of the measure of academic productivity.

Update :
Here is a link to the articles that cite J. E. Hirsch's article - An index to quantify an individual's scientific research output- on h-index via Google Scholar http://scholar.google.com/scholar?q=link:http%3A%2F%2Fwww.pnas.org%2Fcontent%2F102%2F46%2F16569.abstract

