This does not pertain to safety, but it is an interesting view of the CR reliability ratings. CR would have us believe that a car with a half-black circle for reliability (below average) is much less dependable than one with a half-red circle (above average).
Unfortunately, few people ask, "How much less dependable?"
According to CR's 2004 April auto issue page 17, the average problem rate for new vehicles in the last 12 months is 0.17 problems per vehicle. For 3 year old vehicles, it is 0.54 problems per vehicle in the previous 12 months. For 5 year old vehicles it is 0.79 problems per vehicle. For the sake of discussion, I calculated the rates of 2 and 4 year old vehicles to be halfway between the others.
Problem rates averages:
First year: 0.17
Second year: 0.36 (estimated)
Third year: 0.54
Fourth year: 0.67 (estimated)
Fifth year: 0.79
So, the average vehicle has only about 2.5 problems after 5 years of ownership.
A model that is given a half-red circle and an "above average" rating can be from 20% to 40% above the average. A model with a half black circle can be from 20% to 40% below the average. Again, being conservative, I will use the middle of the range and assume 30% better or worse than average.
Total problems for a typical "Above Average" model: 1.8
Total problems for a vehicle 30% below average: 3.3
Taking the difference, we find the typical vehicle rated "Above Average" with a half-red reliability rating from Consumer Reports will have about 1.5 less problems over 5 years of ownership than one rated "Below Average" with a half-black reliability rating. For example, according to page 79, the difference between a Honda Odyssey (about 30% above average) and a Dodge Grand Caravan (just over 20% below average) is probably even less.
Personally, I don't find that to be all that much, even with the rounding and any flaws in my math or logic. Overall, the problem rates are quite small for the average vehicle. Unless you buy one with a full black circle (Much worse than average), you will probably find most new vehicles to be quite reliable over the first 5 years of ownership. I think new cars are so reliable overall that CR and other evaluations of reliability probably exaggerate small differences to hype themselves.
Of course, the other question is how serious does a problem have to be to be considered by a Consumer Reports subscriber that returns a reliability survey. I don't have an answer to that one, and one can debate the scientific merits of the ratings all you want...
Unfortunately, few people ask, "How much less dependable?"
According to CR's 2004 April auto issue page 17, the average problem rate for new vehicles in the last 12 months is 0.17 problems per vehicle. For 3 year old vehicles, it is 0.54 problems per vehicle in the previous 12 months. For 5 year old vehicles it is 0.79 problems per vehicle. For the sake of discussion, I calculated the rates of 2 and 4 year old vehicles to be halfway between the others.
Problem rates averages:
First year: 0.17
Second year: 0.36 (estimated)
Third year: 0.54
Fourth year: 0.67 (estimated)
Fifth year: 0.79
So, the average vehicle has only about 2.5 problems after 5 years of ownership.
A model that is given a half-red circle and an "above average" rating can be from 20% to 40% above the average. A model with a half black circle can be from 20% to 40% below the average. Again, being conservative, I will use the middle of the range and assume 30% better or worse than average.
Total problems for a typical "Above Average" model: 1.8
Total problems for a vehicle 30% below average: 3.3
Taking the difference, we find the typical vehicle rated "Above Average" with a half-red reliability rating from Consumer Reports will have about 1.5 less problems over 5 years of ownership than one rated "Below Average" with a half-black reliability rating. For example, according to page 79, the difference between a Honda Odyssey (about 30% above average) and a Dodge Grand Caravan (just over 20% below average) is probably even less.
Personally, I don't find that to be all that much, even with the rounding and any flaws in my math or logic. Overall, the problem rates are quite small for the average vehicle. Unless you buy one with a full black circle (Much worse than average), you will probably find most new vehicles to be quite reliable over the first 5 years of ownership. I think new cars are so reliable overall that CR and other evaluations of reliability probably exaggerate small differences to hype themselves.
Of course, the other question is how serious does a problem have to be to be considered by a Consumer Reports subscriber that returns a reliability survey. I don't have an answer to that one, and one can debate the scientific merits of the ratings all you want...