Reply To: Pew Research Study of American Jews, 2021

It is true that they count patrilineal descent as Jewish (if the person self-identifies as Jewish) even if maternally (and therefore halachicly) they’re non-Jewish.

But, on the other hand, those who do not identify as Jewish, even though maternally they are Jewish, are counted as non-Jews even though they are halachicly Jewish. Even if their great-grandmother married a Goy and all her descendants identified as Christian, they’re all Jewish if from the maternal line.