Yesterday I read a blog post that had me thinking about countries that start with D. No, seriously.

There are only four of them. But before we get to the countries, here’s the mind game that prompted this post.

1. Pick a number between 1 and 10.
2. Multiply that number by 9.
3. If it’s a two-digit number, add the digits together. (If it’s a one-digit number, do nothing.)
4. Subtract 5.
5. Now take that number and match it to a corresponding letter using the following algorithm: A = 1, B = 2, C = 3, and so on.
6. Now think of a country that starts with that letter.

Are you thinking of Denmark?

Yeah, you and a lot of other people. (Maybe the image primed you a bit…)

There are a few variations of this so-called “mind game.” Sometimes there’s another step that asks you to take the last letter of the country you thought of and then think of an animal that begins with that letter.

Are you thinking of a kangaroo?

I’ve even seen versions that go a step further and ask you to take the last letter of that animal and think of a fruit that begins with that letter.

I hope you’re sitting down for this, but…

Are you thinking of an orange?

The reason this game works at all, of course, is that the person running it forces the listener, via a bit of cool math, to come up with D.

Every. Single. Time.

Don’t believe me?

The trick hinges on the fact that when you multiply any number from 1 to 10 by 9, you get a number with digits that add up to 9. For example, the digits of 18 add up to 9, the digits of 27 add up to 9, and so on.

Mind blown yet?

In other words, there’s no way that you can end up with any letter of the alphabet besides D.

But What About Djibouti?

I admit that I came up with Denmark when I first tried the game.

But then I thought, “What about Djibouti?”

There are four countries that start with D, and yet if you asked 10 Americans, I bet 9 of them would say Denmark.

Well, as it turns out, it’s not quite 9. But it’s still the majority, if my Facebook friends are representative (and they may not be).

Before publishing this post, I shared the above game and waited to see how my friends responded.

A whopping 72% said “Denmark,” but “Djibouti”—to my great surprise—came in second. (Maybe my friends are just up on their Horn of Africa geography…)

A Primer on the Four Countries That Start with D

The four countries that start with D are Denmark, Djibouti, Dominica, and the Dominican Republic. That’s it.

And no, we’re not counting country names in a foreign language, such as Deutschland, the German word for Germany.

Of course, the “mind-reading” trick I mentioned above fails miserably if your listener picks Djibouti, Dominica, or the Dominican Republic. The person asking you to go through the math is banking on your limited geographic knowledge.

In the interest of improving your geographical knowledge, then, here’s a brief rundown of each of the four D countries. (All population stats are July 2017 estimates taken from the CIA’s World Factbook.)

Denmark

Location: Northern Europe

Neighboring country: Germany

Population: 5.6 million

Main language: Danish

Of the four countries that begin with the letter D, this is probably the one you know. It’s in northern Europe, it’s where Legos come from, and it even appears in a famous line from Hamlet: “Something is rotten in the state of Denmark.”

Djibouti

Location: East Africa

Neighboring countries: Eritrea, Ethiopia, Somalia

Population: 865,000

Main languages: French, Arabic

Dominica

Location: the Caribbean

Neighboring countries: none (it’s an island)

Population: 74,000

Main language: English

Dominican Republic

Location: the Caribbean

Neighboring country: Haiti

Population: 10.7 million

Main language: Spanish

Americans and Geography Are Like Oil and Water

So are most Americans really more likely to think of Denmark before Dominica when it comes to countries that start with D?

I think so. And the data suggests that yes, Americans are bad at geography.

The Roper Survey, a 2006 inquiry into geography skills, found that  10% of Americans ages 18 to 24 think that Sudan is in Europe. (It’s not.)

In addition,  fewer than half of those surveyed knew that Sri Lanka is in Asia. (This is the same Sri Lanka that was all over the news in December 2004 due to the tsunami in the Indian Ocean that killed a quarter of a million people.)

Of course, the U.S. education system doesn’t place an emphasis on world geography. And we’re not really lighting it up when it comes to the study of foreign languages, either.

If American students do learn geography in school at all, the focus is invariably on American—and potentially European—geography. Everything else gets left behind.

Think about it: did you study the countries of the Horn of Africa in your tenth-grade world cultures class? I didn’t.

Greg Chun, a former international cultural program developer at technology firms SK Planet and SAP in Seoul, says that other factors are at play, too. “One’s command of geography depends upon a number of factors, including where one now lives, where one grew up, and how one traces her ancestry.”

By this logic, a citizen of tiny Liechtenstein, for example, would have a greater understanding of geography than someone who has grown up in the middle of the United States.

The Puerto Rico Conundrum

To give you an idea of just how bad Americans are at geography, consider this: 46% of Americans do not even know that Puerto Ricans are U.S. citizens.

Those who know that Puerto Ricans are Americans overwhelmingly supported giving aid to Puerto Ricans in the aftermath of Hurricane Maria, while those who don’t were half as likely to support aid.)

Let that sink in.

If we view Puerto Ricans (correctly) as “on our team,” then they might just get the help that they need. If, however, we view them (incorrectly) as “foreign” or “other,” then we’re less likely to help.

One of the ways that journalists, educators, and bloggers can promote geographical understanding is by using comparisons.

For example, this article mentions that Puerto Rico—population 3.1 million—has more people than Vermont, Wyoming, and Alaska combined. I would wager that this comparison has more meaning for you than if you saw only the population statistic.

So if many Americans don’t even know that Puerto Rico is part of the United States, it seems unlikely that they would know (or care) about far-flung countries.

Why Geography Matters

So are you a bad person if you can’t come up with the four countries that start with D?

No, but at the risk of sounding trite, knowledge of the world is crucial for anyone working in a global economy. Knowledge of geography is as useful a skill as knowledge of math, foreign languages, human psychology, and economics.

These fields pervade everything we do.

Michigan State University professor Harm de Blij thinks geography is an essential but often overlooked component of students’ education.

His book Why Geography Matters: More Than Ever makes the case that knowledge of place informs our decisions about the major issues of our time, from climate change to terrorism.

Americans need to be better at geography. But that’s not because we should all join hands in song and live in peace and harmony for all eternity. (Although that certainly beats war and famine.)

It’s because Americans need to know that they’re not the only people in the world. We need to know how other countries’ politics, cultures, and economies affect our own, and vice versa.

Djibouti’s military might may never rival America’s. But at a time when our president says Nambia (repeatedly!) at a meeting with African heads of state, a better facility with maps would go a long way towards knowing what other nations are out there.

And not just countries that start with D, either.

Looking for more trivia? Check out these English words that end in the letter q.