It's been well documented — not that anyone ever questioned the idea — that when it comes to human interactions, men are from Mars, women are from Venus.

Men and women communicate differently, act differently and have different emotional needs. Manifestations of these innate differences aren't confined to the sexes' relationship with one another. Instead, they infuse perceptions and expectations in the outside world, even when it comes to something with no obvious male/female bias: inflation.

"That men and women occasionally see things differently is not a remarkable observation," says Michael Bryan, economist at the Federal Reserve Bank of Cleveland. "But that the sexes could report vastly different perspectives on the rate at which prices are rising over a long period of time is astonishing."

Bryan has studied decades of data on this battle of the sexes, using the University of Michigan Survey of Consumers, a joint survey conducted by the Cleveland Fed and Ohio State University among others. He found that demographics played a role in determining the public's estimates and predictions of inflation.

Those who are rich, married, white and middle-aged have lower inflation perceptions and expectations than those who are poor, single, non-white and young. That seems almost intuitive: Society's "haves" are better positioned to endure cost-of- living increases than the "have-nots."

Yet even after holding income, age, education, race and marital status constant, "men and women hold very different views on the rate at which prices are changing." Bryan writes in a November 2001 commentary, "The Curiously Different Inflation Perspectives of Men and Women." Women consistently think inflation is 1.9 percentage points higher than men, and they expect prices to rise 2.1 percentage points more than men.

What can explain this gender gap?

"I've had a lot of theories over the years, only to see them knocked down," he says.

I know a challenge when I hear one. To help Bryan out, I conducted my own unscientific survey of randomly selected women. The only prerequisite was knowing what CPI stands for.

1. I Am Hausfrau Hear Me Roar

Simply put, women do most of the household shopping. They go to work, schlep the kids to their doctors' appointments, piano lessons and sports practices, go to the supermarket, cook, clean and run the home.

This was one of Bryan's early working hypotheses, which he dismissed as unconvincing. Just because women do a disproportionate amount of the shopping and have "a more accurate perception of price behavior," there is no obvious reason why that perception should be systematically higher or lower than men, he writes.

"Over time prices go up, not down," says Michelle Girard, senior economist at RBS Greenwich Capital Markets Inc. The frequent shopper is "more likely to experience price increases," not to mention anticipate their continuation in the future.

2. Spa Rats

Men and women shop for different stuff. Men make more infrequent and larger purchases: the occasional Porsche, computer or flat-screen TV. Women shop on a regular basis, buying food, clothes and gasoline, but "they use services more than men," Girard says. "My hairdresser raises his prices every year."

Sore subject. If she pays anything close to what I pay, the price of that haircut is secret, not to be shared with any household Martians.

Unlike goods, services aren't traded on global markets — a New York yellow cab doesn't compete with a ride in Shanghai — prices tend to be "sticky," in econospeak.

In the last 20 years, the consumer price index for services (nothing excluded) increased an average 3.4 percent annually. The CPI for commodities rose 2 percent.

3. Worry Bias

When asked about the feminine mystique of inflation, economist Veronique de Rugy, a senior research fellow at the Mercatus Center at George Mason University in Arlington, Virginia, was quick to separate the men from the women.

"It has everything to do with motherhood," she says. "It has to do with worrying."

If higher expectations of inflation aren't borne out by the facts, then the overestimation "must be something else," she says. "It must be a worry bias."

After all, we women "aren't confused by numbers," she says. (If only Larry Summers had told that to the Harvard faculty.)

4. Quality Shoppers

Many items in the CPI are adjusted for quality changes. For example, when the 2008 model year cars come out, the Bureau of Labor Statistics determines how much of the higher sticker price is improved quality and how much of it is an actual price increase.

Any buyers? If the average woman is anything like me, she'll say, fine, I'll take the 2007 model because it's cheaper and has less of that flashy chrome. Can you hear a guy saying that?

We women prefer to make our own quality adjustments, thank you very much.

Even if Bryan comes up with a satisfactory explanation of why women expect higher inflation than men, why does it matter? It matters because Fed policy makers see expectations as a driver of inflation. If women are consistently experiencing and expecting higher inflation, then the Fed needs to do something about it.

Instead of wasting his time speaking to groups of Wall Street bankers, where women are underrepresented, Fed Chairman Ben Bernanke needs to branch out and talk at some Venus gatherings: PTA meetings, Tupperware parties, maybe even the annual conference of the National Organisation for Women.

Better yet, for maximum media penetration he could follow in his predecessor's footsteps and make an appearance on the "The View."

(Caroline Baum, author of "Just What I Said," is a Bloomberg News columnist. The opinions expressed are her own.)