Although the main primary of the Webometrics Ranking is to promote the publication in the Web by Universities and other research related institutions, the web indicators produced allow a comparative analysis with other scientometric or bibliometric indicators.

The tables in this section provide a preliminary overview of a limited number of institutions, but our objective is not to go into detail. On the contrary, the data shows both a global good agreement among rankings and several striking measurements corresponding to a well defined group of countries. The first scenario suggests the web indicators could be useful for scientific evaluation purposes while the second one points out some weakness in the commitment to web dissemination of knowledge.

The number of global rankings available for comparison purposes is very limited, so only six different sources were used for extracting the data. As absolute values are not comparable, all the figures were converted into rankings. The data providers are:

Our own Webometrics Ranking of World Universities (http://www.webometrics.info/) is the basis for the comparison, although the data were segregated into components for the different purposes. Taking into account the data came from the November 2005 round (not the current already updated data published in the main pages of the Ranking), the ranks for size (number of pages) and rich files (documents in pdf, doc, ps or ppt formats) were used for the productivity tables, while the number of external inlinks appears in the Visibility section and the global Webometrics Rank is used for the impact tables.

Essential Science Indicators (http://scientific.thomson.com/products/esi/; http://www.in-cites.com/; http://www.esi-topics.com/) is a powerful database elaborated by The Thomson Corporation that provides number of papers and citations received by those papers for a large number of institutions worldwide. Extracting the universities, merging results from variant names of the same institution and deleting some mistakes, data from August 2005 (covering a period of more than ten years), the ranking of papers was used for productivity while the citations ranking appear in the visibility and impact table.

Google Scholar (http://scholar.google.com) still in a beta phase is providing access to a large (and increasing) number of databases interlinked of bibliographic and webliographic records of scientific papers. During November of 2005 all the records appearing under the institutional domains of the universities were counted and the obtained rank was used as a measure of productivity.

The data for popularity (number of visits) was extracted from the Alexa database (http://www.alexa.com). This system intercepts a large number of visits through its toolbar and spyware distributed almost evenly worldwide. The rank indicates the position of the institution in the global database, although the positions were reorganised by institution (universities) and regionalised (due to geographical bias detected in the Far East area) and finally appear in the visibility tables.

The Academic Ranking of World Universities, updated in 2005 (http://ed.sjtu.edu.cn/ranking.htm) elaborated by the Institute of Higher Education of the Shanghai Jiao Tong University. The combined indicator was recalculated using their own data for providing a unique position to every one of the 500 universities in the list. This position was used as an impact measurement.

The Times Higher World University Rankings 2005 (http://www.thes.co.uk/worldrankings/) consists of only 200 institutions. The rank was also considered as an impact measurement.

Three groups of tables were prepared, including rankings of indicators of different sources. A world list of the Top 50 universities in each category is provided with smaller regional tables with the 20 most relevant institutions of Europe, North America, Latin America, Asia and Oceania (Africa was excluded by practical reasons).

Productivity. The universities are classified by a mathematical combination of the rankings according to their websize, number of rich files, number of papers published in the last ten years and records in the Scholar.

Visibility. The criteria combined include link visibility, number of citations to papers in the ISI database and number of visits (popularity) to the web domain.

Impact. The list is presented according to their position in the Shanghai’s ranking, and the Webometrics, Times and ESI citation rankings are also provided for comparative purposes.

There is a strong perceived correlation among the different lists, especially relevant among the first positioned institutions and between the ESI and the Shanghai rankings. The Times classification appears to be the most divergent one. North American universities are consistently the first ranked according to the different criteria