I would guess by your name that you are somehow affiliated with ND. That is one school where Admissions is very open about the benefit to being a legacy applicant. At ND, they have a target range for legacies in terms of composition of each class, and it hovers around 25%. That being said, a large number of these applicants would be admitted without the extra boost. For some, however, it was the tipping point that got them in. As someone in Admissions told me a few years ago, being a legacy can cure the sick, but it won’t raise the dead. Even with this benefit, the majority of legacy applicants to ND are denied.