If I don't rate my Uber driver, does it reflect negatively or count against him or her?

The Uber rating system is a very misunderstood pass/fail system.   Not rating a driver doesn't hurt him or her, but it doesn't help them either.  

A 5* rating is "GOOD" and reflects positively on the driver's rating.  

Any other rating, 4* or below, is "BAD" and will hurt the driver's rating, and could potentially cost them their job.  

Drivers need to maintain a minimum rating of 4.66 over the last 100 rated rides.  If we drop below that, we face permanent deactivation with no chance for appeal.  

5* + 5* + 5* + 5* + 5* + 5* + 4* + 4* + 4* + 4* = average 4.6 rating = Goodbye Felicia

5* + 5* + 5* + 5* + 5* + 5* + 5* + 5* + 5* + 1* = 4.6

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That said, Lyft's rating system is very similar, however with recent changes, it differs in that all rides are now counted  5* unless you actively rate your driver lower.  No rating = 5* default rating