It is the last taboo. Talking about it is not something a nice girl does in mixed company, it is indelicate, unfeminine.
Many women have been raised to believe that men are "naturally good" at money matters and women are "naturally bad" at money matters. It's not said directly, little girls pick up this idea by osmosis.
Outside the home, for a man to say he wants more money or ask for a raise is acceptable; it goes with the hairy chest and the company car. But women can't say that, they won't even admit it to themselves and they don't want to think about why. Because they've been raised to believe...what? That discussing money will grow hairs on their chest? Or that, being a woman, they don't deserve more money?
I don't know the answer. But I do know that over my last ten years of interviewing women, while researching an ebook about maths and money, called "MONEY STUFF", I asked many women if they would like to be richer.
They all said, "No!" Just like that.
I asked, "You really mean that you wouldn't like more money?"
They said, "Well, just a little bit more."
That's the trouble with women. Women think small scale about money, in terms of housekeeping or being able to order a new kitchen, rather than being able to give a tablet computer to a quarter of a million underprivileged people, as British entrepreneur, Felix Dennis, did recently.
Women need to think bigger, and women need to learn more about money - because they don't get enough of it.
Why do women need more money?
Because a woman might - unexpectedly - find she is the main earner in her family. Marriage isn't always forever, accidents can happen, jobs disappear.
Because the average woman earns up to 20% less than a man who is doing the same job, so no wonder some men still regard women as inferior to themselves.
Because children are the most expensive modern luxury; it costs more to run a child than it does to run a Bentley. To raise an average child costs over £227,000 - and that doesn't include the cost of your time.
Money can help to keep your children happy and well-nourished, both mentally and physically. Money can ensure you are kept clean and warm, clothed, fed and entertained in comfortable surroundings with internet access, street lighting, roads and sewers. Money can promise you with fashion, jewellery, pets and cars if that's what you want.
Zillionaires will tell you there's only one thing more valuable that money and that is your time. But money can buy you quite a lot of that, given a home help, a nanny, a private jet.
Money can do all these marvellous things and that is why men like to have more than their fair share of it.
There's another reason that women need more money. Money brings independence, respect and power.
Exactly what is power?
Many women don't' understand what "power" means, or why they should want it. But in the nursery, power is called, "getting your own way".
In nature, power means physical strength. Rightly or wrongly, money has replaced physical strength as our modern measure of power; it defines our position in the pecking order, which rules our lives as inexorably as physical power does in the animal world of lions, stags or fighting cocks.
In history, think of 16th Century portraits of the bejewelled
Queen Elizabeth I of England in her gem-laden gowns. What is the PR pitch of those portraits? Wealth, prestige, power.
So what's not to like about having power?
The power of the purse means being able to do things without using your own hands. Sweep that floor, dig that pond, catch that plane and privately educate your children to top status level.
The power of the purse can mean privacy, having a room of your own in which to discover yourself, plus time enough to do it.
Money creates the power to do things. You need money to train your ability to act, to sing, to dance, to hit, throw or kick a ball - and to entrance people with your performance. You need money to build a workshop, a church hall, a museum or a university.
Without the power of the purse you might be forever stacking supermarket shelves at night, rather than perhaps learning to getting ideas and making discoveries that will improve your town, your country, your planet.
Purse power - investment - is needed to produce inventions that will improve people's lives. Think of the steam engine, atomic energy, the hearing-aid and the bra.
The really powerful women I know - the big earners - don't waste their lives lying in bed all morning or watching afternoon TV until it changes to evening TV, or drinking themselves stupid (well, not often). They get things done. They improve their business, their community and other people's lives. They find time to do voluntary work.
This is why, as a sex, we women need to raise the bar, to throw away the constricting whalebone corset that is our out-dated attitude to money, lift our focus above the housekeeping purse, stop being frightened of the big noughts, dump lack-of-confidence, man up, get more ambitious about money, and learn more about how to make more.
Best-selling author Shirley Conran has created MONEY STUFF, a new interactive ebook for women to learn about maths and money, available from 5th June.
See more at www.moneystuff.com.
[nb ed: Child cost figures according to research from the Centre for Economic and Business Research, January 2014.]