Similar to how the divorce rate among those who use NFP is less than one percent.
It's good to hear of low divorce rates among American Orthodox. Interestingly I heard from Michael Medved, and he has the links, that the divorce rate for couples (man and woman) who marry for the first time is around 30% according to census bureau statistics. The 50% comes in from those marry two, three, four times.Good to keep in mind when particular people argue that no one takes marriage seriously any more.
While true, this is only half the story. The divorce rate is calculated as the number of divorces in a year divided by the number of marriages. But this is deceiving because the number of marriages was higher in the past than it is today, so this results in a high number, even when the number of divorces is less than 1-2% of the total number of married couples in total.
More interesting is the number of people who have ever been married who have ever been divorced. This number is something like 30%.