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Toyota Age Equivalents
by James Bleeker

The following table provides the estimated ages of when a typical 1999 model by Toyota Motor Corporation will be about as troublesome as a typical 1999 model of selected other manufacturers and lines were at ages 3, 4, 5, 6, and 7 years.

Age Equivalent Estimates for Toyota Motor Corporation

Estimated Ages of When a Typical 1999 Toyota Motor Corporation Model Will be as Problem-Plagued as Typical 1999 Models of Other Automobile Manufacturers, Groups, and Lines Were at Ages 3, 4, 5, 6, and 7 Years

Manufacturer or Group Line Estimated Age of Toyota Model Corresponding to a 3-Year-Old Model of Listed Manufacturer or Line Estimated Age of Toyota Model Corresponding to a 4-Year-Old Model of Listed Manufacturer or Line Estimated Age of Toyota Model Corresponding to a 5-Year-Old Model of Listed Manufacturer or Line Estimated Age of Toyota Model Corresponding to a 6-Year-Old Model of Listed Manufacturer or Line Estimated Age of Toyota Model Corresponding to a 7-Year-Old Model of Listed Manufacturer or Line
Nissan Motor Company 5 years 6 years 8 years 9 years 11 years
Mazda Motor Corporation 9 years 11 years 13 years 16 years 19 years
  Ford 15 years 16 years 18 years 20 years 23 years
  Lincoln 14 years 16 years 19 years 22 years 26 years
  Mercury 15 years 17 years 20 years 22 years 26 years
Ford Motor Company 15 years 17 years 19 years 21 years 24 years
BMW AG 9 years 12 years 20 years 24 years 26 years
Mercedes-Benz 17 years 22 years 24 years 27 years 27 years
  Chrysler 18 years 22 years 26 years 32 years 32 years
  Dodge 17 years 21 years 24 years 29 years 32 years
  Plymouth 13 years 21 years 24 years 32 years 33 years
  Jeep 20 years 23 years 24 years 26 years 34 years
Chrysler Group 17 years 22 years 25 years 29 years 32 years
  Saturn 8 years 13 years 17 years 17 years 17 years
  Buick 14 years 17 years 20 years 23 years 24 years
  Cadillac 22 years 22 years 24 years 29 years 32 years
  Chevrolet 19 years 22 years 25 years 31 years 34 years
  Pontiac 20 years 24 years 27 years 30 years 36 years
  Oldsmobile 20 years 25 years 28 years 33 years 35 years
General Motors Corporation 19 years 22 years 25 years 29 years 33 years
  Audi 15 years 23 years 27 years 31 years 33 years
  Volkswagen 20 years 27 years 31 years 38 years 42 years
Volkswagen AG 19 years 25 years 29 years 35 years 40 years

The computation of these estimated age equivalents is rather involved. (While some PhD theses seem to have been thrown together in a Saturday afternoon, the above estimates were not, as you'll soon see.)

What follows is, in the main, what appeared in a November 2007 article on AutoOnInfo.net.

We begin with the following table of Reliability Score averages for model year 1999.

The Reliability Score Averages for Model Year 1999 

Note      The above Excel table is the original table from the November 2007 article, so it bears the visual shortcomings of the graphics made by earlier Microsoft products.

Next, we plot the Reliability Score averages of Toyota Motor Corporation for each of the above age ranges (2-to-4 years, 3-to-5 years, ..., 4-to-6 years) and make an extrapolation of these plots, a linear regression of degree one. We will first determine an estimate of when a typical 1999 model of Toyota Motor Corporation will be as troublesome as a typical 1999 model of General Motors Corporation at about age 3 years. To do this, we plot GM's Reliability Score average for the first age range (2-to-4 years) and draw a horizontal line. For the x-axis, we use the midpoint of each age range. We have:

Toyota Motor Corporation's Reliability Score Averages for Model-Year-1999 Vehicles for Various Age Ranges, An Extrapolation Thereof, and General Motors' Reliability Score Average for Model-Year-1999 Vehicles at 2-to-4 Years of Age

The equation on the chart is the regression equation for Toyota's extrapolation. From the chart's extrapolation, we see the estimate of when a typical 1999 Toyota model may be as troublesome as a typical 1999 GM model circa age 3 years to be about 19 years. By computation, substituting GM's rounded Reliability Score average of .27 (for age range 2-to-4 years) for y in Toyota's regression equation, we obtain an estimate of 19.0 years. Another way of viewing the result is: If a typical 1999 GM vehicle became unacceptable to own by reason of trouble or risk of trouble at about 3 years old (calendar year 2002 or earlier), then a typical 1999 Toyota vehicle may become unacceptable to own at about age 19.0 years, or circa calendar year 2018.

The next four charts depict similarly derived estimates of age equivalents (with respect to vehicular deterioration) for a typical 1999 model of Toyota corresponding to approximate ages 4 years, 5 years, 6 years, and 7 years of a typical 1999 GM model.

Toyota Motor Corporation's Reliability Score Averages for Model-Year-1999 Vehicles for Various Age Ranges, An Extrapolation Thereof, and General Motors' Reliability Score Average for Model-Year-1999 Vehicles at 3-to-5 Years of Age

Toyota Motor Corporation's Reliability Score Averages for Model-Year-1999 Vehicles for Various Age Ranges, An Extrapolation Thereof, and General Motors' Reliability Score Average for Model-Year-1999 Vehicles at 4-to-6 Years of Age

Toyota Motor Corporation's Reliability Score Averages for Model-Year-1999 Vehicles for Various Age Ranges, An Extrapolation Thereof, and General Motors' Reliability Score Average for Model-Year-1999 Vehicles at 5-to-7 Years of Age

Toyota Motor Corporation's Reliability Score Averages for Model-Year-1999 Vehicles for Various Age Ranges, An Extrapolation Thereof, and General Motors' Reliability Score Average for Model-Year-1999 Vehicles at 6-to-8 Years of Age

From the charts, we see that the estimates of when a typical 1999 Toyota model may be as troublesome as a typical 1999 GM model at about ages 4 years, 5 years, 6 years, and 7 years are about 22 years, 25 years, 29 years, and 33 years, respectively. By computation, substituting GM's rounded Reliability Score averages for y in Toyota's regression equation, we obtain the following estimates of when a typical 1999 Toyota model will be as troublesome as a typical 1999 GM model at ages 4 years, 5 years, 6 years, and 7 years: 22.4 years, 25.5 years, 29.4 years, and 33.1 years, respectively.

Note that each succeeding chart requires an extrapolation farther into the future and consequently each succeeding age-equivalent estimate is less certain.

By substituting the Reliability Score averages for each of the manufacturers and lines into Toyota's regression equation, we obtained the above table of Toyota age-equivalent estimates, rounded to the nearest whole year.

With regard to the computation of Reliability Score averages, I borrow the old summary:

The definition of Reliability Score begins with two observations. First, the symbols in the right-most column of a Consumer Reports auto model reliability table depicts reliability performance of categories (called “trouble spots,” by Consumer Reports) of components of motor vehicles in the approximate age range of 0 to 1 year – the exact age range depending upon when the corresponding model year began and ended and when Consumer Reports stopped accepting returned questionnaires for its compilations. Second, similarly, the second column from the right, the third column, the fourth column, the fifth column, the sixth column, the seventh column, and the eighth column depict reliability performance of the same categories of components in the approximate age ranges of 1 to 2 years, 2 to 3 years, 3 to 4 years, 4 to 5 years, 5 to 6 years, 6 to 7 years, and 7 to 8 years, respectively.

Next, some particular Reliability Scores are defined, from which may be seen a general definition. The Reliability Score RS(The Lexus LS400,1991,7-8) was obtained as follows:

1.   The leftmost column of the Lexus LS400 reliability table in the April 1999 issue of Consumer Reports was selected, as it is this column that rates problem frequencies by “trouble spots” in the 1991 Lexus LS400s that were in the age range of 7-8 years, approximately.

2.  The trouble spots of “Manual Transmission,” “Clutch,” “Brakes” and “Exhaust” were eliminated from this left-most column for reasons discussed in step 1 of the foregoing definitions of Reliability Index Value and Average.

3.   If all of the remaining 12 trouble spots had a Consumer Reports rating, the following was done. First, -1 was ascribed to each of those trouble spots that earned the lowest rating (had the highest frequency of reported auto problems. Second, - ½ was ascribed to each of those trouble spots that earned the second lowest rating (had the second highest frequency of reported auto problems. Third, 0 was ascribed to each of those trouble spots that earned the middle rating (had the third highest frequency of reported auto problems. Fourth, + ½ was ascribed to each of those trouble spots that earned the second highest rating (had the second lowest frequency of reported car problems. Fifth, +1 was ascribed to each of those trouble spots that earned the highest rating (had the lowest frequency of reported auto problems.

Next, the numbers that were obtained in 3 were added together and divided by 12. This value is the Lexus LS400’s Reliability Score:

RS(The Lexus LS400,1991,7-8).

Rather at once, it is seen that this value falls in the closed interval [-1,+1], as is the case for all Reliability Index Values.

While the above computations are for model year 1999, they likely apply to more recent model years as well, since changes in quality occur at a rather glacial pace. See Charts of Annual Shares of Consumer Reports' Used Cars to Avoid.

As the above computations are quite involved, they are not likely to be duplicated soon, and updating for more recent years is additionally complicated by the possibility that Consumer Reports may have changed the definitions of the symbols it uses, which would require an additional examination to determine whether the change, if any, is significant with respect to maintaining uniform Reliability Scores.

Disclosure      Site manager is currently a very small shareholder of Ford Motor Company (2010-04-27). I am not, and have not been, a shareholder of any other motor vehicle manufacturer.

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