The following was posted on SIPA's Admissions Blog on March 8 along with an analysis of the 2017 MIA/MPA applicant pool (emphasis added):
Lastly, decisions will go out in mid-March 2017 on a rolling basis. I can’t give you an exact date, but I can tell you we’re finalizing the review process as I type out this sentence. There are checks and balances in place that the Admissions Office has to do by hand to ensure accurate results, so please be patient with us. As soon as your admissions decision is ready we will email you the news. Just be patient. And good luck to all of our applicants!
http://admissionsblog.sipa.columbia.edu/2017/03/08/a-confidential-look-at-our-fall-2017-applicants/