"Dear Colleagues,

The purpose of this mail is to present our latest working paper, deposited on
July 24, 2014.
http://googlescholardigest.blogspot.com.es/2014/09/about-size-of-google-scholar-playing.html​​

We propose the inextricable task of knowing the size of this huge black hole
looks like Google Scholar (GS). Anyway, as the title of the document
(​​About the size of Google Scholar: playing the numbers), we have begun to
make accounts and using 4 different empirical methods we estimate that the
number of unique documents (different versions of a document are excluded)
should not be less than 160 million (as of May 2014).

Regardless of this particular outcome, which is itself significant (especially
when compared with other scientific databases, and that gives us key clues
about the amount of scientific knowledge that can be searchable, found and
accessed to on the web), even more exciting is the methodological challenge of
this assumption. It has not only forced us to devise various techniques for
measuring the size of this dark object that GS is, but ​also ​applying them
we have shed light, again, on various inconsistencies, uncertainties and
limitations of the search interface tools used by Google. In short, we have
learned more about what Google Scholar does or does not, and we want to share
it with you all.

This research comes at a good time. We are not only almost celebrating the 10th
anniversary of GS but also hearing some voices (from somewhere in Europe…)
finally relying on the use of Google Scholar for scientific evaluation.

Now, when empirical studies
(http://googlescholardigest.blogspot.com.es/p/bibliography.html) demonstrate
every day that Google Scholar and its derivatives

a) measure with similar credit to traditional bibliometric indicators,

b) are the most used products by scientists
(http://www.nature.com/news/online-collaboration-scientists-and-the-social-network-1.15711),​
and​

c) have unfortunately ended up with the competition (Microsoft Academic Search
is in an unexplained hibernation,
http://googlescholardigest.blogspot.com.es/2014/04/empirical-evidences-microsoft-academic-search-dead.html)​.​

seems that certain euphoria unleashed. We are pleased, better late than
never…

However, without wanting to lower the aroused expectations, we emphasize that
the problems of Google Scholar for scientific evaluation are not technical or
methodological (coverage, reliability and validity of the measures, records
filtering performance…). Seminal limitations are those related with:

a) the ease with which GS indicators can be manipulated​
(http://ec3noticias.blogspot.com.es/2014/01/google-scholar-wins-ravesbut-can-it-be.htmt),

b) the transience of the results and measures (in many cases difficult to
replicate stably),

c) the technological dependence on companies that develop tools that come and
go on the consumer product market
(http://ec3noticias.blogspot.com.es/2014/04/la-new-new-horizontes.html-bibliometrics).

Google Scholar enthusiasts are now welcome; meanwhile we will continue
vigorously in which we already proposed several years ago: to reveal with
“data” ​- ​and not mere opinions​ -​, the bowels of Google Scholar,
and to reveal at the same time their strengths and weaknesses. So, like the old
serials published, we can only promise...TO BE CONTINUED…

​Best,​

Enrique Orduña-Malea​
​Polytechnic University of Valencia​

​​Emilio Delgado López-Cózar
Universidad de Granada​" (SCHOLCOMM list)