Looking for a statistic to defend the use of video for corporate
communications. Ideally a study that states a higher retention rate
for video (versus reading)

I've heard that certain of our senses are stronger than others and we
remember more depending on whatsense we are using.  For example take a
look at this:

"We will remember what we hear five times longer than what we see. 
Persistence of Vision and Hearing are instincts that are the basis of
television and movies because images remain on our retina for a split
second (half a second in th case of vision, and five seconds in the
case of hearing). Get it? We remember what we hear five-times or more
longer."

http://speedlearning.org/columnboy.php?title=Is+it+High-kicking%3F

Also:

"Growing evidence also suggests that we remember what we smell longer
than we remember what we hear and see (Berko et al, 1998)."

http://www.4essays.com/essays/INTERPER.HTM

Maybe the case can be made that with video, you not only SEE the
information but you also HEAR the information, which is a higher
retention rate than just seeing it.

Also there are a lot of studies recently stating something to the
effect that we all learn differently.  Some can learn a task by simply
reading it, some need to see it, and some need to actually experience
it hands on.  This last sentence is my opinion and not based on a
study (that I know of at least!)

Let you know if I find anything else.

Bowler-g