Why is the word count of email promotions getting shorter?

I just completed my analysis of June email promotions for this week's issue of All About eMail from Target Marketing magazine. One of the striking numbers to me is how the average word count continues to drop.  Comparing April 2010 data to April 2011, the word count average has dropped to 374 per email, a reduction of 8.1%.

For "repeated" emails, those appearing more than once in the EmailCampaignArchive.com database, the word count drops even more to 235.  That's 37% less than "all" emails.

Clearly shorter email word count isn't a fluke.  It's a trend.