How important is National Merit for top schools?

Colleges disclose their selection criteria in their Common Data Sets. This allows you to see a list of what matters to each college.

For example, U of Chicago:

http://www.collegedata.com/cs/data/college/college_pg02_tmpl.jhtml?schoolId=327

As you can see, the criteria they list as “very important” are academic rigor, recommendations, essay, talent, and character.