'Valid' is used in this instance as defined in the #2 definition of the
second definition.
I did some searching and couldn't trace to a source for this assertion. I did find an article at the wsj by "The Numbers Guy" who also
couldn't find a source for this 20 year old adage.
<snip>
For at least two decades, this number has been a fixture of news articles, marketing websites and books about consumer behavior. And as with many oft-repeated statistics, no one is sure where it originated.
<snip>
In addition to having murky origins, the number appear to be wrong. Several recent surveys suggest that men have nearly equal say on spending, and that when men and women live together, both participate in spending decisions. In a survey conducted last year of nearly 4,000 Americans 16 and older by Futures Co., a London consulting firm, just 37% of women said they have primary responsibility for shopping decisions in their household, while 85% said they have primary or shared responsibility. The respective figures for men were similar: 31% and 84%.
<snip to end of article>
Researchers say so many judgments and emotions go into consumer purchases that it likely isn't possible to measure who makes which household spending decisions.
"{80%} is not a credible figure," says Esther Duflo, an economist at the Massachusetts Institute of Technology who studies consumer behavior. "There just is not one. How would you possibly estimate it?"
The woman who is often mentioned as the "source" for the numbers, CEO of TrendSight Group, Marti Barletta, has a rather
long and arduous blog post describing how she came to to use the 80% figure in 1999 "although there was no primary source for it, it was consistent with the "gestalt" of numbers we did have sources for..." TrendSight group is a marketing strategy firm specializing in marketing based on gender.
This reminds me a lot of the "
commonly known fact" that "A woman over age 40 has a better chance of being killed by a terrorist than of getting married. "
As
Mark Twain said, "It's not what you don't know that kills you, it's what you know for sure that ain't true."
Fortunately, this particular adage doesn't have deadly consequences, unless you're in the marketing business.
