OK, if I answer you, will you answer me about the quote you used?

I think they don't, other than making the already-noted attempt to discriminate between 'mother tongue' users of English and others who may be part of a wider community of users as a second or third language. If you come across any info on this I'd be very interested.

Thanks for the graph, CapK - yes, that does seem to show a fair degree of correlation, doesn't it? I suppose a bar type would also show the comparative values betweeen the languages [hint-hint-emoticon]