You can connect the Google Analytics account associated with your extension to your Extpose account. (How to connect Google Analytics)
After connecting GA account you can see weekly conversion statistics in your dashboard. Also, you can use reports that show you daily installs and traffic sources decomposition.
Data from Google Analytics is a bit inaccurate because adblockers could block analytics even on Chrome web site. The good thing is that this data updates frequently, so you don't have to wait days for Chrome Developer console or Webstore to reflect the latest dynamics.
To protect Google Analytics data, Extpose provides a way to claim extension ownership and hide GA data from everyone else. Just click a "Claim" link in the dashboard.