Check your chapter's number by Jackie Han
A page to help you understand the size of your events in the past:
See also the analyzing section.
Statistics about using your event's short url
For each GDG event, the firefly project (http://gdg.events) creates a short url that tracks which users have used the link. You find the statistics at the firefly url appending
analytics, e.g. gdg.events/78dd40/analytics for GDG DevFest Berlin.