ZD,
“Just because there is an intermarriage doesnt mean the children arent Halachically jewish. If we assume that both men and woman equally intermarry, then the children where the woman is jewish are jewish even though its an intermarriage”
1) Therefore the question “what percentage”. He did not say absolutely none are Jewish.
2) The ratio would decline year after year. Even if the first generation of intermarried a were 50% Jewish because of matrilineal descent, not all her children who intermarry will be females. And it is a gemwtric regression.
All of us her are aware that if the mother is a Jew, then the child is a Jew. But you seem to miss that it has to be continuous