In thisreading reflection, write a couple of brief paragraphs (about 200 words total, but that isn’t strict) about one of the readings.
Summarize the main points of the reading and any prominent arguments/evidence used to support the evidence
Explainhow this reading relates to the course material (does it support something in lecture? is it an example of a general theory? does it advance an argument? etc.)
Describeyour personalanalytical andemotional (if you choose) reactions to the piece.
Again, this is meant to be an informal way for you to engage with the material.
1/16/2019 Be Forewarned: Your Knowledge is Decaying
https://hbr.org/2012/11/be-forewarned-your-knowledge-i 1/3
DECISION MAKING
Be Forewarned: Your Knowledge
is Decaying
by Samuel Arbesman
NOVEMBER 05, 2012
When was the last time you read one of your old textbooks? I bet it’s been awhile. But if you were to
compare the version you studied in school to the most recent edition currently in use — no matter
how recently you graduated — you’d find your version sorely outdated. You shouldn’t be surprised
by this: facts are changing all around us.
Whether it’s what we think is true — the nutritious value of certain foods, the status of Pluto as a
planet, or the number of chromosomes in a single human cell — or even the state of our
surroundings — the population of the planet, the fastest 100-meter dash, or the powers of particle
accelerators — our knowledge is in constant flux.
It turns out knowledge is a lot like radioactive atoms because it decays over time. And when we’re
dealing with large amount of facts and information, we can actually predict how long it will take for
it to spread or decay by applying the laws of mathematics. In fact, there’s even a field of science
called scientometrics that studies such things from a quantitative perspective. We now know that
there is a shape to how knowledge grows and how it spreads through a population. We can also
examine different branches of knowledge — medicine, sociology, etc. — and see how long it takes for
half of what we know in these fields to be overturned or rendered obsolete. For example, in the
fields of hepatitis and cirrhosis — medical fields related to diseases of the liver — researchers have
found that half of the knowledge was overturned in about 45 years.
1/16/2019 Be Forewarned: Your Knowledge is Decaying
https://hbr.org/2012/11/be-forewarned-your-knowledge-i 2/3
Of course, some of what we learn will probably never change in our lifetime, such as the number of
continents. And some will change often, such as the number the stock market closed at yesterday.
But those aren’t the facts we should be worried about. We should be concerned most about the facts
that change slowly, the facts that change over the course of years or decades or an entire lifetime —
these are called mesofacts — and examples include everything from the populations of cities to what
dinosaurs looked like (they had feathers?).
We need to recognize that mesofacts are far more common than we may realize — but it’s not easy. In
hindsight they may seem obvious, but they’re not. Since mesofacts decay very slowly, we often fail
to recognize their change around us. This is a problem.
A friend of mine, for example, was speaking recently with an older hedge fund manager who began a
story with the following: “Since we all know that there are 4 billion people on the planet…” This is a
problem. This finance expert is dead wrong — in fact, he’s billions of people off (we’re now over
seven billio