...Some economists claim you don’t need economic models to understand the world. You just need data. Let the numbers do the talking. But numbers are mute. They only speak with our help. And what we say they are saying, inevitably involves a model of the world. But the model is veiled by the simplicity of the numbers.In today’s Washington Post, [https://www.washingtonpost.com/local/dc-hunger-report/2020/10/01/1770590c-0337-11eb-8879-7663b816bfa5_story.html] as I write these words, there is a story with the headline:
District’s food insecurity rate estimated to be 16 percent, up from 10.6 percent before pandemic
I don’t know what food insecurity is. The article does not explain it. Presumably it is related to hunger. That it has increased by such a large amount is disturbing but it’s hard to know just how disturbing without knowing what exactly is meant by food insecurity and more importantly, how the measure of 16 percent was determined. I suspect most people read the story and concluded, as the story suggests we should, that food insecurity is up a little over 50% in the nation’s capital. Definitely alarming.
The story does link to a report from the Office of Planning in the Mayor’s office of Washington, DC. I click through and open the report. The first paragraph mentions:
the critical importance of ensuring that every resident in the District of Columbia has access to healthy, affordable, and culturally appropriate food.
Is that the definition of food insecurity? Not quite. That is explained in the second paragraph which reads in its entirety:
“Food insecurity” is a term defined by the U.S. Department of Agriculture that refers to a lack of consistent access to enough food for an active, healthy life.
[https://www.ers.usda.gov/topics/food-nutrition-assistance/food-security-in-the-us/definitions-of-food-security.aspx]
Food insecurity is definitely a bad thing. Or at least it could be depending on how it is defined. But as this makes clear, it’s a concept that is loose, vague, and indeterminate. Food insecurity has some connection to hunger and malnutrition but measuring it is inevitably a subjective exercise to quantify a subjective concept and give it the patina of an objective measure. When we see a comparison between 16% and 10.6% our brains see something that looks objective.
And is there anything more objective than the decimal point? When last year’s food insecurity measure for Washington DC was calculated, it wasn’t rounded up to 11 or made vague by saying “a little more than 10%.” It was 10.6%. Most jokes about economists are cruel. Perhaps the cruelest is this one:
Q: How do you know macroeconomists have a sense of humor?
A: They use decimal points.
Meaning that the macroeconomics forecaster isn’t content to predict that unemployment will be higher or lower next year or next quarter or next month relative to the present. The forecaster will usually predict the precise number carried out to at least one decimal point to give the forecast the air of precision that sometimes comes with scientific measurement. Decimal points, to quote W.S. Gilbert of Gilbert and Sullivan, “give artistic verisimilitude to an otherwise bald and unconvincing narrative.”
And it turns out, when you dig deeper into the report on food insecurity, the 16 percent number is a projection. The report says that food insecurity is projected to be at least 16 percent. I want to suggest that when you see the headline, your mind decides that there is a reliable objective fact that food insecurity is at least 50% worse than it was before. But that’s not an objective fact. What it really means requires some digging and even some digging may not be enough.
The desire for certainty, the desire to turn a matrix into a scalar, a chart of attributes into a single number, is not just understandable, it’s often the only way to make progress on a problem. If food insecurity is indeed on the rise and policies are put in place to help reduce food insecurity, measurement gives you some chance to know if the policies helped or hurt.
Without measurement, as Lord Kelvin points out, we can’t know if our knowledge is reliable. That’s the upside of measurement. The downside is that inevitably, almost any measurement we use embodies a set of assumptions that are easily forgotten.
I’m about 66 inches from the bottom of my feet to the highest point on my head. I say “about” because precise measurement is difficult. It depends on how I stand and the challenge of measuring anything with perfect precision. But that I am 5’6” is reasonably described as a fact, partly because any deviation from that precision is quite small relative to the correct, unobserved, not easily ascertained exact height I am right this minute on October 2, 2020. It’s also reasonably described as a fact because you as the consumer of that fact have probably used a tape measure or a ruler or yardstick and are very aware of getting an accurate measure of height within say 1/64th of an inch.
The same would be true of the temperature right now in your house or outside. The weather app on my phone says it is 63 degrees Fahrenheit in my house. That is surely not the exact temperature just outside my front door or even 30 feet away from it. There’s no decimal point and the precise temperature will vary whether it is measured over asphalt in the street or in the yard where the grass reacts differently to sunlight. But like height, when I tell you the temperature is 63 that’s close enough for deciding whether to wear a sweater, short-sleeves, or a heavy parka if you are planning on leaving the house.
But is the 16% food insecurity rate for Washington DC a fact? It looks like a fact because it’s a number. Our brains associate numbers with what we call facts, numbers that have standards of measurement that we use or have used often, like measuring height or observing the temperature on a thermometer. But many things that look like objective facts are what we might call scientism — things that have the appearance of science but without the reliability of science. Our brain struggles to keep them apart.
I don’t know whether it is a good idea or a bad idea to try to quantify a subjective concept like hunger, poor access to healthy food, or poor access to affordable food. What I am saying here is that your brain struggles to remember that a number like 16% as a measure of food insecurity is not a simple fact like height or temperature. But your brain, if it’s like mine, is prone to treating it like a simple fact...
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