The filter uses something like the old INK geo-targeting algo which attempts to define the market at which the page is aimed. This is also used on worldwide searches which will sometimes give the effect of UK Yahoo worldwide page 1 SERPs and filtered SERPs being identical on some searches - though both will be different from the .com results. However, if you look at a phrase usually targeted at the US on .co.uk you will see the filtered results can be very different.
[edited by: makemetop at 11:58 am (utc) on Mar. 13, 2004]
