Edit: I used to subscribe, and as a result received their surveys occasionally. They seemed pretty well done, but people are people and probably aren’t always objective in their reporting.
We weigh the severity of each type of problem to create a predicted reliability score for each vehicle, from 1 to 100. We use that information to give reliability ratings for every major mainstream vehicle. (The reliability rating is then combined with data collected from our track testing, as well as our owner satisfaction survey results and safety data, to calculate each test vehicle’s Overall Score.)
They don’t get very granular, but they give a fairly detailed overview of the methodology here:
https://www.consumerreports.org/cars/car-reliability-owner-satisfaction/who-makes-the-most-reliable-cars-a7824554938/
Edit: I used to subscribe, and as a result received their surveys occasionally. They seemed pretty well done, but people are people and probably aren’t always objective in their reporting.
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They send a survey to their subscribers.
The next paragraph states: