Do number of installs spike when you publish a new version to the Android Market?

I just published a new release (the first update) of Cow Tipping (  Just in the time since the update 36 hours ago the stats are saying that the number of installs has increased about 50 times it's normal rate.  Seriously... it's averaged like 10 or 20 a day and yesterday there were about 500.  WHY?!?  Are these (a) new downloads or (b) a combination of new downloads and reinstallations of the latest version by existing users?  Seems like an enormous spike. Is there anything that would affect the number of installs around the time you publish a new version?

Don't know the answers to these questions.  Someone out there might.