[jlokier]

IP address is one of many signals used to build a statistical profile.

It doesn't match you exactly to the other persons behind the same NAT, but it adds some information, raising the likelihood of ad coincidences a little. I have no idea how much. It's likely to depend on which IP address, and other tracking statistics.

If you have diligently blocked lots of tracking state, then IP address will be a relatively stronger signal, and this might (ironically) increase the likelihood of ad coincidences.