NPE Rates

A recently published study of extra-pair paternity (EPP), often called NPEs, in the Netherlands and Belgium shows that historical rates were low overall (∼1%) but higher for urban populations than rural and for those with low socioeconomic status. Combining the two the rate was ∼5.9% among urban families with low socioeconomic status.
That means for the 15 couplings back to your great-great-grandparents there would be a 14% chance of at least one NPE at the overall average 1%, but a 60% chance for urban families with low socioeconomic status.
The table shows the probability a person has one or more NPEs, cumulatively back for a specified number of generations, starting with parents at one generation.

Generations	Couplings	1% NPE Rate	2% NPE Rate	6% NPE Rate
1	1	1	2	6
2	3	3	6	17
3	7	7	13	35
4	15	14	26	60
5	31	27	47	85
6	63	47	72	98
7	127	72	92	100
8	255	92	99	100
9	511	99	100	100
10	1023	100	100	100