I've never understood this tactic. Specifying a range seems like a good way to underprice yourself. If you give a range, the recruiter will simply assume that your current salary is very close to the bottom of the range.
Now, if you mean that you give a range of previous salaries, the recruiter will know your best previous salary anyway. And they'll probably knock a fair bit off the top assuming you're padding.
> I prefer to give a range than specify individually.
FWIW, this is likely almost as bad for you in the negotiation as giving the number. You will simply always get offers towards the bottom of your range. It is better to refuse to answer, and just say you're looking for a market rate salary for this role.
Giving the number doesn't have to be bad for you. (But it can be.)
But yeah, never give any range. Not when talking about previous compensation, and not when talking about what you want. Just give them straight up numbers, if you give anything at all.
And you should definitely give them a number about how much you want to be paid. You want to set the first reference point. And yes, that means you will have to do your own due diligence about how much the market can currently bear for your (interviewing) skills. But you need to know these numbers anyway.
But it's not a dilemma. There's nothing wrong with saying "I don't disclose my past salary. It's personal. Let's focus on this job, and if you make me an offer, we can discuss that."
Some ethics test. The employer is already failing at ethics by asking this in the first place, so I have no problem lying to them. This is no different than them asking if you have kids, if you're married, etc.
Then for the employer, will you decrease the salary to match previous low rates or wages? Or will you pay him/her the market rate regardless?
Personally, I have always been asked how much I made at previous places. I prefer to give a range than specify individually.