Doing some research in preparation for a draft answer to CESR's Call for Evidence on standard reporting formats, I was curious to find out how much of the world's capitalisation is already covered by an XBRL mandate. I've thrown together a list of jurisdictions provided by Mike Willis that either already have a mandatory scheme of XBRL disclosure for issuers in operation or decided about its introduction. Using country weights of the MSCI World Index for developed countries (i.e. without China or India and others, both of which have or will soon have a scheme in place), this adds up to slightly above 60% of the "developed" world's equity capitalisation that is already covered by a mandatory XBRL disclosure scheme today.
While this is an encouragingly large share, it is still some ways away from the 90+% that I reckon to be necessary to encourage global investors to migrate the information infrastructure of their analytical processes to XBRL. Bringing the EU's market cap on board would bring us substantially closer to that important threshold.