Here come two resources to help understand the resemblances and differences among indexes to measure the Information Society.
The first one:
Sciadas, G. (2004). International Benchmarking for the Information Society. Busan: ITU.
http://www.itu.int/osg/spu/ni/digitalbridges/docs/background/BDB-intl-indices.pdf
http://www.itu.int/osg/spu/ni/digitalbridges/docs/background/BDB-intl-indices.pdf
is a comparison of all (or almost, who knows one year after) the existing indexes
The second one:
International Telecommunication Union. (2005). Measuring Digital Opportunity. Seoul: ITU.
http://www.itu.int/osg/spu/ni/wsisbridges/linked_docs/Background_papers/Measuring_Digital_Opp_Revised_31_Oct_2005.pdf
http://www.itu.int/osg/spu/ni/wsisbridges/linked_docs/Background_papers/Measuring_Digital_Opp_Revised_31_Oct_2005.pdf
is an essay led by the International Telecommunication Union to collaborate internationally to measure the digital divide: the Digital Opportunity Index