I don't understand why that would be the case. With a long-term rate staying stable, either a couple is going to break up, or they're not. Pushing forward the b

I don't understand why that would be the case. With a long-term rate staying stable, either a couple is going to break up, or they're not. Pushing forward the breakups would not alter the long-term rate, just as pushing backward the breakups (as long as they're still within the window observed by the study) doesn't lower the long-term rate.