Changing the subject, does anyone know how the worldwide numbers of (native) Spanish speakers stack up against either English or Chinese? And how the numbers are changing over time?

Short answer: around 200 million Native Spanish speakers, up from maybe 150 million over the last 25 years - compared to maybe 700-1000 million Chinese speakers, and only 100 million German speakers.

Long answer: see the posting on wider issues of Language Demographics
http://wordsmith.org/board/showflat.pl?Cat=&Board=miscellany&Number=16487&page=0&view=collapsed&sb=5