I referred a friend, when will my rate increase?

In order to receive the referral boost, both you and your referral need to be actively mining at the same time. It should appear shortly after your friend created their account. You'll see your friend's gamertag and miner status on the Earn tab.

If after 10 minutes you're still not getting a boost, then have your friend enter your referral backup code on their Access Code page in Settings.