The One-Number Trap

Editor’s Note - Originally published at The Roots of Liberty March 2014.

Back in the 1980s, the local blood bank, which would visit our company every quarter for donations, offered free cholesterol screenings for those who donated blood. We'd get a number and a reference note that indicated the cut-off between good and not-good was 200. A lovely number, that 200. Nice and round and easy to remember, and it really stood out when your cholesterol reading dropped from 201 to 199. Today, we know that cholesterol scores are a bit more complicated than that single number. There are "good" cholesterol and "bad" cholesterol measurements, and while the two are totaled to get your total score, the individual numbers have desired ranges. There is also a triglyceride score, and there are of course all sorts of other numbers in a standard blood profile. Yet when I've interacted with people who open the subject of health up, that one total cholesterol score always seems to be the lead in the conversation. I've heard, on more than a few occasions, declarations of triumph from people who managed to tick that leading "2" down to a "1." The balance of the information doesn't seem to be nearly as important. It's an easy trap to reduce assessment of one's health to one number, especially if the yes-no divide is so round and obvious.

In the late 1990s, we were informed of another important health number - Body Mass Index (BMI). BMI is a simple measure, computed by dividing your mass in kilograms by the square of your height in meters. The BMI formula had been around for 150 years, but relatively few knew about it until the government started a health information campaign that focused on it. Coinciding with the start of that campaign was a revision of the cut-off between good and not-good, from 27.8 to 25, and an establishment of 30 as the cut-off for "obese." We thus had and have another nice, round number to tell us whether we are healthy or unhealthy. On top of that, we have a second number, which like the cholesterol "200," has the added feature of a changing first digit representing the ultimate line of demarcation. Cross from 29.9 to 30.1, and you're no longer merely "overweight" but "obese." And what an ugly word "obese" is. It conjures images of fat rolls, thunder thighs, flattened footwear and people lumbering down the street wheezing with every breath. But, a six-foot tall person who weighs 225 lbs has a BMI of 30.5, and I doubt that the word "obese" would be the first to cross your mind should you see some of that height and weight walking down the street. The BMI measure also makes no allowance for physical fitness or age, and while some of the BMI calculator websites do note that BMI can overestimate the "fatness" of athletes and underestimate the "fatness" of seniors, such vague warnings aren't as neat and tidy as the nice round "25" or "30." For measuring body fat, BMI may be quick and easy, and over a broad population may return definitive results in the aggregate, but it can lack accuracy for individuals.

Consider the Dow Jones Industrial Average (DJIA), a number that's almost invariably the first shared by business reporters on the radio, television and in the press. It's even the first number listed by the iPhone stock app. How many readers know that the DJIA, or the "Dow" as many call it, represents not the entire market, but 30 specific large companies? And, while those 30 companies do make up about a quarter of publicly traded stocks, the Dow doesn't reflect the entire stock market, nor does it reflect smaller companies. Yet the Dow is the number people first think of when they contemplate how the market is performing, and when the index ticks its thousands digit over, it's considered a Big Deal. There are many other indices out there, including the S&P 500, the NYSE composite and the NASDAQ index, and some more accurately measure the overall market. I bet, however far more average folks on the street could ballpark what the Dow's current value is than any of those other indices, and I bet that many of them will consider it an important sign when the Dow maintains above 16,000. Again, a single number, with nice round thresholds. And, given that the Dow's a price-weighted formula, a number that doesn't even have meaning to most lay people.

We can find other examples of single numbers and strong psychological reactions when those numbers tick over a first digit. It was a big deal when the unemployment rate held stubbornly above 8%, and also a big deal when it dropped from 7.0% to 6.9%. Yet only wonks know that the widely reported unemployment number involves excluding "discouraged" workers from the computation. Discouraged workers are those who are deemed by the bean counters as having dropped out of the labor force, and therefore are no longer "unemployed." Obviously, there must be some distinction made between those who would normally work but can't find a job and those who may be stay-at-home parents, retired from the workforce, independently wealthy, housewives or househusbands or not-working domestic partners, and the like. But, the determination of who's "discouraged" also involves how long someone has been without a job and other factors. The point here is that the widely reported unemployment rate isn't as simple as one might believe. There are also other unemployment rates, including one that counts all those "discouraged" workers, but it's rarely reported or reported only as an aside to the primary figure. The unemployment rate that's reported is also chock-full of guesses, because actual data gathering takes months. Numbers are revised after the fact, but they're given about as much heed as newspaper corrections and retractions.

The global warming alarmists cautioned us strongly that, if the atmospheric carbon dioxide concentration exceeded 400 parts per million, we'd cross a "tipping point" from which there would be no return. Catastrophically Bad Things were sure to follow. Setting aside the strength of the science or lack thereof in that debate, or whether there's a tipping point at all, why must the tipping point be a round number like 400? Why not 393 or 407? Does Mother Nature have a preference for the base-10 numbering system and changes in first digits? What if we had six fingers on each hand and therefore used a base-12 numerical system? 294 isn't nice and round like 400 is, nor is it memorable, nor does it seem "important." If you were told the magic number for your total cholesterol was 148, would you stress much about missing the goal if your cholesterol was 149?

To be fair, round numbers make things simpler and easier to remember, and can serve as motivators. If you're trying to lose weight, crossing 10 lb thresholds can give your spirit a lift. If you're battling your cholesterol level, the psychological effect of knocking that leading "2" down to a "1" can be strong and heartening. Round numbers can serve a positive purpose in this regard. But, just as they can work positively, they can also be demotivating. Suppose you hit a "wall" in your efforts to knock your cholesterol down. Suppose you've dropped it from 254 to 207. Or, suppose you're on a long-term effort to bring your weight down. You've shed 23 lbs, are down to 164, and hit a plateau. Putting too much emphasis on round numbers might cause some to give up, to say "I tried and failed" and fall back to bad habits instead of celebrating their success. And, putting too much emphasis on individual numbers can also mislead if they displace deeper consideration . Sure, your cholesterol might be 196, but you might be one of those people who have naturally good cholesterol and you use that number to deflect the fact that you're carrying 50 pounds more than you should. Or, you see the unemployment rate drop from 7.0% to 6.9% and cheer the improving health of the economy, despite the accompanying report that says most of the drop came from people leaving the workforce.

We can look to blame a society that's some say has ADHD, where the sound-bite culture of last decade has given way to the 140 character limit of Twitter, for the phenomenon of single numbers. But the easy and lazy path has always been part of human society. If, in our busy and harried lives, we can find a yardstick that gives us a quick and obvious yes/no answer, why not make use of it? Yet very often that "one-number" assessment is a trap that can mislead or deceive. Knowing the one number and the magic threshold does us little good if we don't understand at least some of what underlies that number. If the round number motivates you, by all means, set the goal. But don't let the lure of quick and easy deflect you from deeper understanding and critical thought. Ignorance may be bliss, but knowledge is king.