Here's [1] a paper on information density vs speed of speech, done by the University of Lyon. I am not sure how accurate their methods are, but they seem to believe that some languages convey more information per syllable and for 5 out of 7 languages, that ones with lower information density are spoken faster. Note that the sample size was only 59 and only compared how fast 20 different texts were read out, all silences that lasted longer than 150 ms were edited out as well.

[1] http://www.ddl.ish-lyon.cnrs.fr/fulltext/pellegrino/Pellegri...