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, and the number of available positions at each program to find the best possible outcome for each participant.
The algorithm starts with an attempt to place an applicant into the program that is most preferred on the applicant's list. Each applicant's Rank Order List is traversed "downwards", from most preferred program to least preferred, until the first program is reached at which the applicant can be tentatively matched, or until the applicant's list of choices is exhausted. Each program accepts applicants "upwards" on its Rank Order List, continually removing less preferred matches in favor of more preferred applicants, until the program is matched to the most preferred applicants who wish to be matched to the program.
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, even if it was the only applicant available to you in the Match.
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 based on how highly you think an applicant will rank your program, you may not get the best possible result for your program.
How do I submit a Rank Order List?
Programs must submit and certify their Rank Order Lists online in the NMS Match System by the Rank Order List deadline. The Rankings User Guide includes information on how to:
- Add an applicant to your Rank Order List
- Delete an applicant from your Rank Order List
- Reorder an applicant on your Rank Order List
- Import your Rank Order List from a file
- Certify your Rank Order List
- Print your Rank Order List
Can I change my rankings after certifying my list?
Yes. Even if you have already certified a Rank Order List you can return at any time to make changes until the Rank Order List deadline.
If you make changes to a list after it has been certified, you simply have to certify the list again before the deadline in order for it to be used in the Match.Related Links:
What do I do if I have no acceptable applicants to rank?
If a program has positions available to begin in 2022 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 program from the Match if the program has positions available.
Programs that certify no ranks in Phase I will be carried over automatically to offer their positions in Phase II. Programs that certify no ranks in Phase II will be carried over to the Post-Match Process.Related Links:
Can I control the distribution or composition of applicants that are matched with my program?
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 school attended or location of residence. To accomplish this, you must divide the program's available positions into separate categories, designate how many positions are to be allocated to each category, and submit separate program Rank Order Lists for each category of position.
Multiple Lists can be submitted only in Phase I of the Match. This feature is not available in Phase II of the Match.Related Links: