We're using 10% as a very conservative estimate actually. We've been measuring adblock data for 9 months now across several hundred sites, many of which are very large. The current average blockrate across all these publishers is 26.1%. These are the guys who are so acutely affected that they signed up to us in the first place, but it gives you a good idea.

A fair estimate of a minimum value is the block rate on sites that are non-techie, e.g., lifestyle (12% blockrate) and news (16% blockrate).

We'll be doing another post soon revealing all these numbers and our methodology in collecting them in detail.

Good point about the rate varying a lot based on the audience - I imagine that tech sites have it worst for blocking rates.

I wonder how the rates vary for tablet/mobile viewing? I'd guess fewer users manage to block ads on these devices?

Oh, and blocking rates on mobile/tablet is very low, probably consisting of ISP-level adblocking. That will shortly change though - the adblock community is hard at work creating mobile versions.

The rate is actually highest on gaming-related sites. I guess that audience is usually sufficiently technical, and is also habitually bombarded with aggressive advertising.

Have any of your customers used the metrics they gleaned to size up an ad-blocker white-listing offer themselves?

Not so far as we are aware. Not many sites have gone down the whitelisting route, for the kind of reasons discussed in the post above. That said, lots of our customers are discovering just how badly they are affected. Some sites have more than 64% of their visitors blocking their ads, and are facing extinction.

The metrics you provide are certainly useful in putting low ad-revenue in some context for a business.