# Single metric you need to care – Or do you?

This is the next article in the series I started last month on a popular customer metric – Net Promoter Score.

Let us discuss today another famous single metric that most of us know and use – BMI or Body Mass Index. For long it  has been used by commoners and practitioners as the single metric to determine whether a person is overweight or not.

Well is that single metric relevant to all? Is that relevant today? Or as an inquisitive high school student asked, “is it relevant at all?”.

Youth Radio’s Bria Bryant tells her quest when she started questioning her doctor’s assertion that she was overweight,

The standard height to weight ratio is called the BMI — short for Body-Mass-Index. The problem is, the BMI is only based on one type of body. From Belgium. In the 19th century, a Belgian mathematician named Adolphe Quetelet came up with the formula based off of height and weight. Then, 150 years later, it became the preferred method of measuring if a person was too thick or thin. The BMI is cheap, fast and simple.

But it’s got a lot of problems. For instance, the BMI categories don’t account for muscle weighing more than fat or for ethnic differences. A spokesperson for the National Institute of Health said the most common complaint is people being misclassified as overweight.

Later Bria finds there are other better ways to measure health than a single generic number.

Same is true for the single metric under discussion here – it is calculated using esoteric math, defined for different period and set of businesses and does not take into account other factors like market dynamics, competition, customer needs and technology shifts.

However, like BMI, businesses small and large ask their customers the “Ultimate Question” and treating the score as absolute.

Like Bria says about BMI, this metric is cheap, fast and simple and also irrlevant.

But do you ask such questions like the smart high school student did? Or accept it s gospel because it was published in a prestigious journal and proposed by someone in position?