Algorithm & Rankings


How the Algorithm Works

  • How does the Match algorithm work?

    The matching algorithm uses the applicant Rank Order Lists, the program Rank Order Lists for each track offered in CASPR, and the number of available positions at each track to find the best possible outcome for each participant.

    The algorithm starts with an attempt to place an applicant into the track that is most preferred on the applicant's list. Each applicant's Rank Order List is traversed "downwards", from most preferred track to least preferred, until the first track is reached at which the applicant can be tentatively matched, or until the applicant's list of choices is exhausted. Each track accepts applicants "upwards" on its Rank Order List, continually removing less preferred matches in favor of more preferred applicants, until the track is matched to the most preferred applicants who wish to be matched to the track.

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Ranking Strategy

  • What is the best strategy for ranking?

    In order to get your best possible result, you should rank your choices in order of your true preferences. Rank all applicants that you would be willing to accept. Do not rank any applicant that you would not want to be matched to your program under any circumstances.

    The algorithm is specifically designed to give each participant their best result if they rank their choices in order of true preference. Using any other strategy may cause you to get a worse result for your program. For example, if you decide to order your preferences by how highly you think an applicant will rank your program, you may not get the best possible result for your program.

Submit Rankings

  • What should I do if an applicant appears on my Rank Order List as "Withdrawn"?

    Applicants who are withdrawn will be indicated with a Withdrawn flag. Withdrawn applicants may change their status and decide to participate in CASPR at any time until the Rank Order List deadline. Therefore, if you planned to rank an applicant who is now withdrawn, you are strongly encouraged to leave the withdrawn applicant on the Rank Order List.

    If you leave the withdrawn applicant on the list and the applicant is reinstated prior to the deadline, that ranking will be used in the Match. If the applicant remains withdrawn, that ranking will not be used in the Match, and the Rank Order List will be processed as if you had not ranked the withdrawn applicant.

    If you have any questions concerning the status of an applicant in CASPR, you should contact the applicant directly.

Special Cases

  • What do I do if I have no acceptable applicants to rank?

    If a track has positions available to begin in 2024 that you would like to fill but has no acceptable applicants to rank, you should certify a Rank Order List with no ranks. Do not withdraw the track from CASPR if the track has positions available.

    Tracks that certify no ranks in the Match will be carried over automatically to offer their positions in MPII. Tracks that certify no ranks in MPII will be carried over to the Post-Match Process.

  • Can I control the distribution or composition of applicants that are matched with my track?

    Yes, using the Multiple List feature available in the NMS Match System.

    The Multiple List feature helps programs recruit a particular distribution or "mix" of applicants based on different applicant characteristics, such as college attended or location of residence. To accomplish this, you must divide the track's available positions into separate categories, designate how many positions are to be allocated to each category, and submit separate Rank Order Lists for each category of position.

    Multiple Lists can be submitted only in the Match . This feature is not available in MPII.

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