Millennial here, I’ve noticed a lot of Stephanies, Sams, Alexes, Chloes, and Michelles. Matthew seemed like a particularly popular one - at one point we had 3 Matthews in the same class (about 25 students), and I had 2 Matthews in my immediate friend group in college.

Edit: Rachel/Rachael was another common one, had a couple of those in my friend group at one point too