Waiting for review

If youre a developer who has an app in Itunes Connect with state "wait for review"
this site may give you hints about the waiting time (or how many work is to do for the reviewers :) ):
https://developer.apple.com/appstore/resources/approval/

Theres a widget on the right site that shows something like this:

App Store Review Status
Percentage of submissions reviewed within the last 7 days

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83%

New Apps

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87%

App Updates