st: Re: SSC archive stats

[Kit Baum <baum@bc.edu>]

David,

I'm afraid that my prior explanations of this issue have been lost in  
the mists of time; my earliest post on Statalist @ HSPH (Jan 2001)  
says 'please see prior month's explanation', but the archives do not  
go back to 2000, and not even Google can find them. So I will try to  
reconstruct the logic.

The web server records every "hit" on an ado-file. ado-files are part  
of a package, which may contain a single ado- (and hlp-) file or may  
contain several or many indeed (e.g. egenmore). A 'score' should not  
be inflated by an author's inclusion of many files in a package, but  
we don't track packages; we track hits on individual ado files. Many  
ado files are multiply authored, and we want each author to receive  
credit for his or her work. So we have one file--an extract from the  
web server log
/http://fmwww.bc.edu/fmrc/reports/report.ssc.html
which says that, e.g., the single file xtabond2.ado was requested 478  
times last month.

From the RePEc templates that define the SSC Archive, we generate  
another file (with perl)* in which each record contains the name of  
one ado-file, the SSC package of which it is a part, the number of  
ado-files in that package and an author's name. There is a record for  
each author|ado combination. So for instance your xtabond2 records in  
this file look like
XTABOND2      /repec/bocode/x/xtabond2.ado      2      David Roodman
XTABOND2      /repec/bocode/x/xtab2_p.ado      2      David Roodman
defining a package which has two components and one author.

Stata then reads the first file (containing the web server log  
excerpt) and merges the second file on the URL field shared by both  
files (the URL from which that ado may be downloaded at SSC). npkghit  
is generated as nhit/nmods -- so if xtabond2.ado and xtab2_p were  
both downloaded 478 times, npkghit would be 478 as well. But last  
month, xtab2_p was downloaded only 393 times, so npkghit is now  
potentially fractional (and for xtabond2 is 435.5). We then collapse  
this file to compute the sum of npkghit by(author package). This  
gives us the first listing distributed in my monthly emails, which  
shows e.g.
   2.    435.50              David Roodman            XTABOND2

We then collapse to compute the sum of npkghit by(author) to generate  
the second listing, e.g.
   6.             David Roodman     594.25
which reflects the totals from the several packages you have authored  
on SSC.

In contrast to the citation-count literature fashionable among tenure  
and promotion committees, I do not give each author of a package with  
N authors 1/Nth of the hits; I give each author all the hits.

So where are these fractions coming from? Recall that when you 'ssc  
install xtabond2, replace' Stata is smart--it only downloads the  
files which have changed. You updated xtabond2.ado but did not update  
xtab2_p.ado recently. Those updating their copies of xtabond2  
installed only one file, while those installing it for the first time  
installed two. That explains why the 'hit counts' are not equal for  
all files in a package. (If people are downloading files from a web  
browser--even to just look at them on the screen--this would also be  
the case; they might look at the main .ado and not be interested in  
ancillary files).

Historical note: the one-page Stata program that does this  
manipulation is named 'forthedean.do', written to satisfy a UK  
economist who thought these stats would be appreciated by the Dean.

Now that I have explained this, I should be able to find the  
explanation in the Statalist archives for the next five years or so!

Cheers
Kit

* Note to Bill Gould: this perl program predated Stata's -file-  
command. If I wrote it today, I'd do it in Stata. It couldn't readily  
be done at the time I started crunching these numbers.

Kit Baum, Boston College Economics
http://ideas.repec.org/e/pba1.html


On Oct 18, 2005, at 5:45 PM, David Roodman wrote:


> Kit, is there documentation somewhere for how you massage the SSC  
> download stats? How do the fractions come about in the number of  
> hits? Thanks much.
>
> --David
>
>
>
> David Roodman
>
> Research Fellow
>
> Center for Global Development
>
> 1776 Massachusetts Ave. NW
>
> Washington, DC 20036
>
> droodman@cgdev.org
>
> +1 (202) 416-0723
>
> fax: +1 (202) 416-0750
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