So should I lie!

there are a lot of people around who shouldn't have had children

This is a worryingly authoritarian point of view.

Oh, I like the "because..." answer, too.

Another good one, IMO, is "What concern could it possibly be of yours?"

But again, up to you. Lots of good ideas here!

First, I agree it's terribly rude - and insensitive (what if you were trying and having a hard time?)! IMO, you would be totally justified in saying, "None of your business!"

However, since I'm sure you want to be more polite than that (unlike these thoughtless people who ask that question), I think you should choose one or more of the responses that have been suggested here. I favor the ones in the "Why do you ask?"/"Excuse me?"/"I beg your pardon?' category. But, of course, it's up to you.

I definitely wouldn't lie thought. You don't have to, and it would just lead to more questions, advice, and perhaps arguments.

Simply reply, "because" and go right on with other matters being discussed. Their question was rude, nosy and inappropriate. You owe them no explanation at all!

What Baggs or Bridgeit said!
Absolutely do not lie - nobody’s business but yours!

Yes Gaunt47 I remember reading about that survey. No idea where.
I asked my mother if she would have had children if she had her time again. I asked because she favoured her first born and it was so obvious. She said she wanted one and got 5 due to my father refusing to use protection and taking her before she had time to use the cap.
I used to be asked a lot in my 30s if I had children. I said, maybe but I need a husband first.
Now the question is do you have any family ? I say yes, 2 stepsons and 5 grandchildren. Smug me.
It just never happened but I never had a terrible yearning.
And it’s not only women anyway. Do childless men get asked the same ? Or as much any way ?
I don’t think there is a need to lie. Or explain, nothing at all. Nobody’s business. A simple no, no children should suffice.

Back in the '70s, a widely syndicated agony aunt in north America asked her readers: if you could have your time over again, would you still have children? In the days before emails she apparently had a huge response, around 70% replied "no".
I agree with the comments up thread that there are a lot of people around who shouldn't have had children.
Aren't we lucky to live in an age when we have a choice whether to have children, or not?

There is nothing wrong with not wanting children. My daughter never wanted children, she says she is not maternal and enjoys her life too much. She said she is selfish and didn't want anything to prevent her from doing what she wanted when she wanted. She has horses and dogs and a career she loves. I actually admire her for sticking to her guns and staying child free. There is an expectation that we should have children, why?

And of course they are not allowed to ask that anymore at job interviews.

Or just say 'I never really wanted my own, but love other people's'. True, polite and no awkward feelings on either side then.

Yea another good one Baggs?

Good idea, bridgeit. Or perhaps "I beg your pardon?"

A good strong, EXCUSE ME ? is another good way of stopping invasive/ impertinent questions .

Hmm, I don't like it when someone says to me to get a cat so I won't be lonely. I'm not lonely. I don't want a cat, the cost, the responsibility. When I had to put my cat down due to her illness I emphatically said DO NOT GET ME A KITTEN to replace Meggy. I'm glad they listened.
Why did I only have one child? I just tell the truth, I had a boy, I wanted a boy and did not want to take the chance of having a girl. Shocks the s**t outta people. It's fun.
But really don't lie, I also say I don't do children, that's a good shocker too. I don't know, have some fun with it, freak em out.

It is rude to ask you such a question. I wouldn't lie, I would just say "I'm sorry, I don't like to talk about it" and let them make of that what they will. It is absolutely no business of anyone else but yourself

So insensitive to ask that question, I would answer either, I don't discuss that, it's private or say no comment and wait for the awkward moment to pass.

I like the term I’m child free through choice!!

I would say that I had other things planned for my life and leave it at that

‘Why do you need to know’ would be my answer.

One more strategy....
Smile innocently and give them a deliberately nonsensical reply..."Well, as you well know, some people have children and some people don't....we happen to be among the latter!"

It will take them at least two seconds to digest that you didn't actually give an answer, plus another few seconds to decide what to do about it...but before they come in for the next round, you'll get a chance to change the subject and bombard them with some annoying questions of your own

This is a very personal question. You don't have to explain! When someone asks why you don't have children say "I just don't!" and leave it at that. You don't have to be polite to people who ask rude questions.

What an odd question and very rude. It's really no one's business why you decided not to have children. I would just say you just decided having children wasn't for you and shut the conveesation down.

My uncle has an elegant way to skip unwanted questions - he just says pass. Or ‘ pass next question‘

"I just never felt the push and I've never regretted my decision."

"I forgot to have them"