"When I use a word," Humpty Dumpty said in a rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."
"The question is," said Alice, "whether you can make words mean so many different things."
Even if it's not answered, a natural question that arises in almost every news story about some quantifiable phenomenon -- which we might label X -- is "How many X?"
Sometimes the question is phrased, "What is the incidence, percentage, or rate of X?"
Since stories are more newsworthy when this number or rate has changed significantly, there is a strong media tendency to look for large changes in X. Often, however, these large changes are spurious, the result of using a flexible yardstick to measure X.
Here are a few recent examples.
There was a recent spate of stories about the rise in the maternal death rate in this country. As has been widely reported, awareness that maternal deaths were not all being recorded has increased over the years. In an effort to correct this, new guidelines were instituted in 1999 and 2003.
The Centers for Disease Control report "Maternal Mortality and Related Concepts" spelled these out:
"... the [new coding guidelines] introduced new details and categories in the cause-of-death titles associated with pregnancy, childbirth, and the puerperium ... the U.S. Standard Certificate of Death was revised to ask explicitly whether any female death was associated with pregnancy, instead of relying on the person filling out the form to voluntarily provide that information."
These redefinitions of maternal mortality had the predicted effect of leading to a higher incidence of reported maternal deaths.
Not surprisingly, these upticks occurred in 1999 and 2003. Some of the increase over the last decade or so may have reflected real change, but much of it seems to have been due to the redefinition. It should go without saying that however sliced, the rate is scandalously high.
Another recent story, this time from the U.K., illustrates the same point. The Conservative Party claimed that crime in various districts had risen significantly under the Labor Party, more than tripling in one district.
As with maternal morality, there was a change in the protocols for reporting crime in 2002. One of the differences is that before this date police had decided on their own whether to classify a crime as violent.
After this date a crime was automatically classified as violent if the victim said it was, and victims are more likely than police to view any sort of criminal action against them as violent.
As Mark Easton, winner of a statistical excellence in journalism award, observed, "The numbers they use don't compare like with like, they've ignored big warnings plastered over the official statistics telling people not to try and compare the two sets of numbers."
Autism is another case in point. There has been a significant increase in reported cases of autism in recent years. However, as numerous organizations, including the Centers for Disease Control, the American Medical Association, the Institute of Medicine, and a special court associated with the U.S. Court of Federal Claims have found repeatedly, there is no credible evidence that thimerosal-containing vaccines cause autism.
This is obviously a very complex topic, and the reasons for the reported increase remain elusive.
Nevertheless, many experts attribute at least part of the increase to two factors: 1) a widening of the definition of autism to include Asperger's syndrome and a variety of other "autism-spectrum disorders" and 2) a keener awareness of these disorders and a more vigilant search for them.
The incidence of human trafficking is also dependent on (changes in) the definition. The strict definition codified in the 2000 U.N. Palermo protocol requires that an unwilling person, whether by fraud or coercion, be transported for the purposes of exploitation, either sexual or labor-related (both very serious crimes). This statement seems clear and literal.
But there are other definitions, one of them the U.K.'s 2003 Sexual Offenses Act, in which trafficking includes the voluntary (i.e., no coercion, trickery, or force) travel of adult sex workers looking for a higher income. The law has some much needed protections, especially for children, but if interpreted sufficiently loosely, it may encompass all forms of prostitution.
Using the strict definition of trafficking, the relatively few successful prosecutions suggest that the number of such cases in the U.S. and U.K. is much, much lower (probably by an order of magnitude or two) than many of the estimates that have been published. The U.K. Act, especially its very loose interpretation, probably derives more from a moralistic aversion to voluntary prostitution than to an effective, focused effort to put an end to trafficking and sexual slavery.
Of course, redefinition isn't always wrong, as long as its proponents are clear about what they're doing. Thus, "Define your terms" is one of the most basic pieces of advice given to those interested in constructing logical arguments. "Don't equivocate" is a related suggestion for good logical hygiene.
That is, don't start out talking about the incidence of stomach cancer and then later say that stomach problems are becoming epidemic without making clear that you're now including food poisoning as a stomach problem.
Unfortunately, too many people, among them politicians and zealous activists of various stripes, ignore the above commonsense advice and instead follow the counsel of Humpty Dumpty. And we all know what happened to him.
John Allen Paulos, a professor of mathematics at Temple University in Philadelphia, is the author of the best-sellers "Innumeracy" and "A Mathematician Reads the Newspaper," as well as, most recently, "Irreligion: A Mathematician Explains Why the Arguments for God Just Don't Add Up." He's on Twitter (twitter.com/johnallenpaulos), and his "Who's Counting?" column on ABCNews.com appears the first weekend of every month.