# Understanding Numbers

**UNDERSTANDING NUMBERS, an introductory essay to Richard Saul Wurman's book Understanding USA**An ant makes its way across the lawn. It has no idea what lies beyond the blades of grass in front of it. We are like ants when we look at numbers. We might understand what we can see, but the rest of our garden is a mysterious jungle. Yet America defines itself with numbers: from the #1 superpower, past the million men marching and the billions of burgers sold, to the trillions of our national debt. The mysterious jungle starts somewhere between a million and a billion. Million, billion, trillion; such little changes in the words hide huge differences in the quantities. If we define ourselves with numbers, shouldn't we try to understand them a little better? How much bigger than a billion is a trillion? One thousand times. Three zeros bigger. It's a number so big, it needs to be seen in a human context before we can really grasp its size. So, we might say: It's the year 0, the beginning of the first millennium, and you have a trillion dollars to spend, at the rate of a million dollars a day. At just before three years, you've reached a billion. You keep spending, and now you are in the year 2001. You still have 737 years to go, spending a million every day, before you reach the end of your trillion dollar pile. We can see that in our minds because we know the length of a day, we can imagine spending a million dollars and we know all about millenniums at the moment. The elements of this word picture are ones we recognize. The charts in Understanding USA are pictures of numbers. Pictures help us to see numbers and to begin to understand what they mean. In these pages information architects have made pictures of time, money, distance, storage capacity, bandwidth by examining the numbers, and making them visible. Not only are some of these numbers big, but sometimes one set of statistics about a certain subject will disagree with a second set about the same subject. "Round numbers are always false" wrote Samuel Johnson. Today, round numbers are often more believable, even though we may have the computing power to state any number right down to the last insignificant digit. Right now (exactly 12:24 EDT on March 26th, 2001) the U.S. Census home page tells me that the population of the U.S. is 283,875,134. The precision of those last three numbers is astonishing! How do they know that? Well... they guessâ€”they call it making a projectionâ€”based on a formula of how many people are being born and how many are dying in a given time period. A mouse click away at the U.N. Population website, that too-precise guess of America's population by the Census Bureau has risen to 284,911,000. (At least they admit the guess by rounding off the last three numbers.) The U.N. number is a difference of enough people to populate a city the size of Detroit, currently the 10th largest in the country. To understand numbers we must ask questions: What's the source? Is it impartial? What would Planned Parenthood's population number be? Some scientists say that ants do not sleep. If they don't sleep, they don't dream. And if they don't dream, they have no imagination. Understanding numbers is part imagination, part scepticism, part wonder.