Do you know what your colleagues earn?
Sex, religion and politics - the old taboos about what you can discuss in polite company have long since disappeared.
These days it seems only one question still has the power to bring conversation screeching to a standstill: how much do you earn?
We have been asking people from all walks of life how much they earn; you can try our quiz here to see what we found out.
We've been met with astonished glares, polite refusals, evasive generalities, embarrassed sniggers - and silence. Hardly anyone wants to reveal what they earn.
And yet everyone is interested in other people's pay.
Professor Andrew Oswald of Warwick University thinks this may be a natural Darwinian human trait. "It appears that subconsciously, sometimes even consciously, humans are obsessed with where they lie in the pay distribution," he says.
But most of us have no idea where we fit in.
Luckily, the Office for National Statistics collects the data for us. A comparison of the earnings of full-time employees is illuminating - and quite different to some people's preconceptions.
When we asked people how much they thought a full-time employee in the exact middle of the pay distribution would earn, their guesses spanned a vast range: £17,000, said one; £50,000 said another (this guess was from an insurance broker).
In fact, the mid point is £25,800. Does that make you feel better or worse about your own pay?
People had even less idea about how much those towards the upper end of the earnings distribution earn. Most of those we spoke to wildly over-estimated.
They thought you would need to be earning hundreds of thousands to be in the top 10% of salary earners. But in fact you are in the top 10% of full-time employees if you are paid over £51,400.
Although these figures provide an incomplete picture in that they don't take into account part-time work or self-employment, they do bring up interesting points of comparison.
But for many of us, the comparison we are really interested in is how much those around us are earning - the person sat at the desk opposite.
And this is something that is much harder to find out, especially for workers in the private sector. In the public sector, the pay scale, at least, is normally readily available, even if you don't know where people sit on that scale.
Pay secrecy can be damaging according to some experts. Professor Marilyn Davidson from Manchester Business School says part of the reason why women earn less than men is because they are more likely to accept the pay they are offered without trying to negotiate a higher figure.
But if they knew that male colleagues were earning more, they might act differently.
"The big secrecy thing is another factor that sustains gender inequalities," she says.
Some workers have even been bound by secrecy clauses in their contracts, but this is soon to change.
A spokesman for the Government Equalities Office says: "From October 2010 the Equality Act will make pay 'gagging' clauses unenforceable so that companies will no longer be able to stop employees discussing their salaries with colleagues in order to find out if they are being discriminated against."
But would we really be happier if we knew how much those around us were getting paid?
Andrew Oswald thinks not. He argues that if we were more open about our pay there would be a lot more unhappiness.
"Being low down a pay distribution hurts people a lot more than it helps to be high up," he maintains.
But if we can't yet tell you the pay of named individuals, we can at least look at the average earnings for particular occupations.
How much do people in different jobs earn? Try our quiz. You may be surprised by some of the figures.
Can Pay, Will Pay: broadcast on BBC Radio 4 at 0900 BST on Thursday, 16 September and Friday, 17 September. BBC Radio 4 debate about pay and tax: 1700 BST on Sunday, 19 September.