<p>I would think that Common App would not affect ED that much, since a first choice is a first choice whether or not its on common app.</p>
<p>Only new people coming because of Common App are people who abuse ED for the sake of have a better chance at any random reach, rather than actually liking the school in particular. </p>
<p>Those people may have picked a different school in the past thinking “Columbia is a waste of time cause I can’t reuse the app for other schools”</p>
<p>But you don’t need to worry about these people cause they probably aren’t very strong candidates anyways. Otherwise, they’d be taking ED much more seriously.</p>