The reliabilities of all model years of the Chevrolet Malibu and the Ford Fusion can be measured using the PPMY index which is defined as problems reported per thousand vehicles per Year:
PPMY = P / S / Y * 1000,
where P = total problems reported during the life of a particular model year; S = total units sold of the model year; Y = years since the model year has been on the market (the age of the vehicle). The index can also be written as:
PPMY = [Problems / (Sales/1000)] / Age.
A bigger PPMY index indicates less reliability of the given model year cars. For example, the most problematic model year of the Chevrolet Malibu is the 2004 Chevrolet Malibu. This model had a total of 132,403 cars sold in the United States and had 1,818 problems reported as of today. The PPMY index can be calculated as:
PPMY = [Problems / (Sales/1000)] / Age = [1,818 / (132,403/1000)] / 14 = 0.98.
Similarly, the most problematic model year of the Ford Fusion is the 2010 Ford Fusion. It had a total of 249,794 cars sold in the United States and had 4,715 problems reported as of today. The PPMY index of this model can be calculated as:
PPMY = [Problems / (Sales/1000)] / Age = [4,715 / (249,794/1000)] / 8 = 2.36.
The complete results for the recent model years of Chevrolet Malibu and Ford Fusion are shown in Table 1 and Table 2, respectively.
| Malibu Model Year | Problems Reported | Sales [1] | Age | PPMY Index |
|---|---|---|---|---|
| 2017 | 50 | 182,736 | 1 | 0.27 |
| 2016 | 145 | 237,426 | 2 | 0.31 |
| 2015 | 91 | 209,918 | 3 | 0.14 |
| 2014 | 158 | 156,086 | 4 | 0.25 |
| 2013 | 558 | 211,357 | 5 | 0.53 |
| 2012 | 673 | 225,801 | 6 | 0.50 |
| 2011 | 878 | 211,055 | 7 | 0.59 |
| 2010 | 1,397 | 183,784 | 8 | 0.95 |
| 2009 | 1,364 | 176,816 | 9 | 0.86 |
| 2008 | 1,079 | 155,433 | 10 | 0.69 |
| 2007 | 1,087 | 129,234 | 11 | 0.76 |
| 2006 | 1,455 | 177,262 | 12 | 0.68 |
| 2005 | 1,556 | 212,400 | 13 | 0.56 |
| 2004 | 1,818 | 132,403 | 14 | 0.98 |
| 2003 | 669 | 177,260 | 15 | 0.25 |
| 2002 | 637 | 144,947 | 16 | 0.27 |
| Fusion Model Year | Problems Reported | Sales | Age | PPMY Index |
|---|---|---|---|---|
| 2017 | 115 | 215,612 | 1 | 0.53 |
| 2016 | 197 | 277,383 | 2 | 0.36 |
| 2015 | 237 | 186,055 | 3 | 0.42 |
| 2014 | 482 | 264,915 | 4 | 0.45 |
| 2013 | 982 | 218,176 | 5 | 0.90 |
| 2012 | 1,489 | 296,093 | 6 | 0.84 |
| 2011 | 2,245 | 198,596 | 7 | 1.61 |
| 2010 | 4,715 | 249,794 | 8 | 2.36 |
| 2009 | 691 | 103,478 | 9 | 0.74 |
| 2008 | 1,061 | 137,991 | 10 | 0.77 |
| 2007 | 953 | 146,797 | 11 | 0.59 |
| 2006 | 700 | 125,637 | 12 | 0.46 |
To study the aggregated reliabilities of the Chevrolet Malibu and Ford Fusion vehicles, we use the PPM index which is defined as:
PPM = Total Problems / (Total Sales/1000),
Where the total problems in the equation is the total number of problems reported for all model years listed in Table 1 (Chevrolet Malibu, 2002 to 2017) and Table 2 (Ford Fusion, 2006 to 2017); The total sales in the equation is the the total number of vehicles sold in the United States for all model years in Table 1 and Table 2. The results are shown in Table 3.
| Car Model | Chevrolet Malibu | Ford Fusion |
|---|---|---|
| Model years | 2002 to 2017 | 2006 to 2017 |
| Total Problems Reported | 13,615 | 13,867 |
| Total Sales | 2,923,918 | 2,420,527 |
| PPM | 4.66 |
5.73 |
| Note: A smaller PPM value suggests better reliability. | ||