File:Car Manufacturer Quality in 2010 by Infrequency of Trouble-Prone Cars.png

English: Car Manufacturer Quality in 2010 by Infrequency of Trouble-Prone Cars

To form a car-manufacturer quality measure from Consumer Reports' 2010 list of Worst Cars, the first step is to count each manufacturer's entries on the list. Each model year of each model is treated as a separate entry.

Next, as the number of automobile models sold by a car manufacturer varies greatly from maker to maker, it is necessary to take account of the fact that a manufacturer 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 of a manufacturer, as well as a variability in model data sufficiency, the number of a manufacturer's entries in CR's 2010 Worst-Cars list is divided by the total number of overall reliability ratings for the manufacturer 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.

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 car manufacturer and is achieved only when a manufacturer has no entry on the Worst-Cars list.

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

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# .

For a Google Knol that summarizes car manufacturer product quality from 1975 to 2010, visit "Car Quality from 1975 to 2010 - A History of U.S. Automobile Manufacturer Quality Ranks" at http://knol.google.com/k/james-bleeker/car-quality-from-1975-to-2010-a-history/3o3u27f0whd6k/9# .