File:Brand Quality in 2010 by Infrequency of Trouble-Prone Models.png

English: Car Brand Quality in 2010 by Infrequency of Trouble-Prone Models

To form a brand quality measure from the 2010 list of Consumer Reports' Worst Cars, the first step is to count each brand's entries on the list. Each model year of each model is treated as a separate entry. For the 2010 computations, only entries from the 6 most-recent model years are counted, for the reason explained in the following paragraph.

Next, as the number of automobile models sold under a brand name varies greatly from brand to brand, it is necessary to take account of the fact that a brand with more models has a greater opportunity to have more model years of low quality. To compensate for a possibly inflated, or deflated, frequency of trouble-prone model years within a brand, as well as a variability in model data sufficiency, the number of a brand's entries in CR's 2010 Worst-Cars list is divided by the total number of overall reliability ratings for the brand found in the reliability charts of the same issue of Consumer Reports. The overall reliability ratings are found in the Used-Car-Verdicts row of the 2010 reliability charts. As the 2010 reliability charts are limited to the 6 most-recent model years, the count of a brand's entries on the Worst-Cars list is limited to the 6 most-recent model years as well.

By the method of computation, this quality measure begins with 0 and may run to a value some greater than 1. The value of 0 is the highest quality rating attainable by a brand and is achieved only when a brand has no entry on the Worst-Cars list.

The quality ranking of the car brands by the foregoing computations, together with their quality ratings, is given in the bar graph above. Only those brands with at least 5 overall CR reliability ratings are included.

Important Point: If the Toyota-engineered Pontiac Vibe is deleted from the Pontiac's count, the Pontiac brand would appear as the 3rd worst brand in the above graph.

For a Google Knol that summarizes the changes in car brand and manufacturer ranking by this quality measure from 1990 to 2010, visit http://knol.google.com/k/james-bleeker/automobile-quality-by-car-brand-and/3o3u27f0whd6k/2?hd=ns# .