10 Bogus -- And Widely Believed -- Statistics

Numbers are all around us, especially in the news: A new drug has a 72 percent success rate in treating a disease (but only in patients under 35), while the president enjoys a 48 percent approval rating, even though according to a 2010 poll, almost one in five of the estimated 314 million Americans believe he is Muslim.

We hear statistics all the time, and science studies are often based on them. While some cynics dismiss all statistics as easily manipulated (the famous “there are lies, damned lies and statistics” quote), the truth is that statistics are important and indeed essential to understanding the world around us.

Numbers can be wrong for many reasons, including mistakes, miscalculations, different studies using different definitions, bias in promoting political or social agendas, and, of course, outright fraud. Often, the statistics themselves are correct; it’s how those numbers are interpreted. After all, a glass can be both half full and half empty, depending on how you look at it.

Here are 10 examples of spectacularly flawed statistics that are (or have been) influential and widely believed.

"The teen pregnancy rate has been high for years, and is on the rise."

Worrying about “kids today” is a time-honored tradition. Every generation wrings their hands and laments the wild, immoral and reckless ways of today’s wayward youth. The sky-high rate of teen pregnancy is often cited as a prominent example, along with a list of suspected corrupting influences such as sex-saturated TV shows and music lyrics.

It’s also wrong; the fact is that teen pregnancy is low and has been dropping. Data from the Centers for Disease Control and Prevention’s National Center for Health Statistics found that the birth rate for U.S. teenagers (ages 15 to 19) fell 6 percent in 2009, the lowest level ever recorded in nearly seven decades of tracking teenage childbearing.

The report, “Births: Preliminary Data for 2009” found that the rate for the youngest teenagers, 10-14 years, fell from 0.6 to 0.5 per 1,000, also the lowest level ever reported. The birth rate for teenagers 15-17 years declined 7 percent to 20.1 per 1,000. This rate dropped 9 percent from 2007 (22.1) to 2009, and was 48 percent lower than the rate reported in 1991. In fact, teen pregnancy has dropped 39 percent since its peak in 1990, partly because the most recent studies report that 87 percent of boys and 79 percent of girls use birth control.

"There are XX number of gays in America."

How many homosexual men and women are there in the United States? It’s hard to say. Accurately counting the number of gays is fraught with difficulty for many reasons, including that different researchers use different definitions (Who do we count as gay? Anyone who has sex with someone of the same gender? Only those who self-identify as gay? Bisexuals?), and because sexual activity is private and surveys must rely on often-biased self reports.

Estimates of the percentage of gays by Alfred Kinsey from the 1930s and 1940s concluded that about one in ten American men were more or less exclusively homosexual. This 10 percent estimate, though controversial in some quarters, was widely quoted and circulated for decades.

In his book, “Damned Lies and Statistics,” Joel Best, professor and chair of sociology and criminal justice at the University of Delaware, noted that, “Later surveys, based on more representative samples, have concluded that the one-in-ten estimate exaggerated the amount of homosexuality; typically, they find the 3 to 6 percent of males (and a lower percentage of females) have had significant homosexual experience at some point.... and that the incidence of homosexuality among adults is lower—between 1 and 3 percent.”

A 2011 study by UCLA demographer Gary Gates of the Williams Institute on Sexual Orientation Law and Public Policy concluded that America has approximately 4 million homosexual adults, representing about 1.7 percent of the population.

"Up until recently in human history, our forefathers usually died by age 40."

Most of us have, at one time or another, heard someone talk about how our forefathers died so much younger than we do today. Sometimes, for example, it’s used to help explain why many women got married in their teens centuries ago; after all, they had to get started with families early since they’d be dead by 40! According to the National Center for Health Statistics, life expectancy for American men in 1907 was only 45 years, though by 1957 it rose to 66. However, this does not mean that our great-grandfathers rarely lived into their fifties.

In fact maximum human lifespan -- which is not the same as life expectancy -- has remained more or less the same for thousands of years. The inclusion of high infant mortality rates in calculating life expectancy creates the mistaken impression that earlier generations died at a young age. For those with a shaky understanding of statistics, the problem is that giving an average age at which people died tells us almost nothing about the age at which an individual person living at the time might expect to die. The idea that our forefathers routinely died young (say, at age 40) has no basis in historical fact.

Speaking of dying by 40...

"A woman over 40 is more likely to be killed by a terrorist than get married."

This statistic, in wide circulation since the 1980s, is really, really bogus. As the ever-reliable folks at the rumor-debunking website Snopes.com noted, this little nugget first appeared in a June 1986 article in “Newsweek” magazine titled “Too Late for Prince Charming?” which melodramatically (and inaccurately) claimed that women over forty with university degrees are more “likely to be killed by a terrorist: they have a minuscule 2.6 percent probability of tying the knot.”

The 2.6 percent statistic came from a badly flawed 1985 study which, according to Barbara Mikkelson of Snopes.com, “was contradicted by a U.S. Census Bureau report from about that same time which found... that women at age 40 had a 23 percent chance (at marriage), not 2.6%” The original reference to being killed by a terrorist was, of course, a bit of creative hyperbole not meant to be taken literally.

It’s difficult to calculate a precise percentage chance of women over 40 marrying because there are so many factors involved. Women (and career-minded women in particular) are waiting until later in their lives to get married and have children -- to mention that many of them are either happy being single or are in long-term committed relationships and don’t feel the need to legally “legitimize” their relationships with marriage. In any event, women over 40 (college educated or not) are far more likely to marry than be killed by a terrorist.

Read more at Discovery News