Tom Turpin
Professor of
Purdue University


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Counting people and insects are difficult jobs

It's a census year. As has been the case since 1790, every 10 years the U.S. government tries to count the number of people living in this country. This activity is mandated in Article I, Section II of the U.S. Constitution.

The purpose of the census is to have a numerical basis for proportioning the congressional representatives and members of the Electoral College between states. Federal marshals who visited every house made the original count. Today the data collection is conducted by the U.S. Census Bureau and involves sending a questionnaire to every house. The questionnaire involves more than the six simple questions of the original census. Questions regarding the economy, crime, employment, health, housing and other areas are now part of the census.

Every questionnaire is supposed to be filled out and returned to the Census Bureau.
If the census is not returned, someone will come to your house to gather the information. According to U.S. law, population totals must be submitted to the president by Dec. 31 of the census year.

It takes a lot of money and people to conduct a census in modern times. But if history is any indication, it seems that even with all the effort and money that goes into the census some people will not be happy with the resulting data.

I guess I am a little surprised that human population counts are not accurate. After all, humans have been counting things, including living organisms, for eons. Of course, errors can always creep in either when doing the actual count or when the numbers are tabulated.

But generally it would seem that we could count ourselves accurately enough for government work. But apparently not. Certainly the hue and cry of media pundits relative to the counting process would indicate otherwise.

The reason is simple. Many federal dollars are appropriated for programs based on census population numbers. So if the group you represent is somehow undercounted, the result is that fewer dollars would be available to support the cause. And that, friends, is reason enough to cry foul!

I suppose that it goes without saying that if we can't count the number of humans accurately that counting insects would be an even more difficult task. After all, insects are small and hard to see. Insects hide and fly away when approached by census-takers. And insects do not fill out questionnaires!

As it turns out, however, accurate counts of insects can be obtained, but the counts are generally done in limited areas. For example, counting aphids on the section of a leaf, borers in a stalk of corn or fruit flies in a laboratory vial. But even counting insects in a small area is a problem when the insects can move around. So entomologists use chemicals or cold temperatures to kill or anesthetize the insects before attempting a count.

Mostly though, insect scientists determine insect numbers through a process known as sampling. That means that counts are made in a limited area and then used to estimate the numbers in a larger area. Of course, even if the count in a limited area is correct the larger estimate might not be.

Statisticians thus hedge their bets and attach a probability of error range to a number developed in such a way. And that is why political pollsters always mention the margin of error relative to their predictions. As do scientists when they report results of experiments.

So how many people live in the U.S. anyway? Well, the first census in 1790 reported 3,929,214 people. As of Jan. 12, 2010, according to the U.S. population clock, there were 308,474,934 people in the U.S. Hopefully the current U.S. census will count all of those who are still alive as well as all of the new babies. But if the naysayers are correct, we probably won't.

When it comes to the number of insects, scientists just make some calculated guesses. For instance, there are more insects in a square mile than all the people on the earth. Or there are 70 pounds of insect flesh for each pound of human flesh. We don't even know how many species of insects have been named. Around 1,000,000, according to some estimates.

World-famous entomologist E. O. Wilson, the ant man, states that there are 10^18 insects on the surface of the earth. That is a million billion insects, or as others have calculated, 1.5 billion insects for each person on the earth. I don't know about you, but even without an accurate census or margin of error estimates for those numbers one thing is clear to me. There are a lot more insects than humans on this earth!



Writer: Tom Turpin
Editor: Olivia Maddox