arod
Unregistered User
(6/7/00 5:53:13 pm)
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Ranking Backups
I have been asking around (w/o much success) about how exactly the match algorithm works. If I have a
strong indication that my home institution wants me and I choose to use this as a backup where should I put
them in the rank list? If they rank me high and I rank them let's say 9 or 10 is there any way I will get screwed
and not match? Any input on the strategy of ranking a backup would be appreciated. Good Luck to all
Kent
Unregistered User
(6/7/00 7:41:22 pm)
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Matching algorithm
Nobody understands this beast! Actually, it's been well written about and has been used since the 1950s. The
nuts and bolts are that you submit a rank list of the places you would like to go and the programs submit a
rank list of the people they want. The computer matches the lists as best it can, that is, the programs get
their best picks and the candidates get their best picks, too. The basic strategy is two-fold--applicants
accept positions UP their list and programs accept applicants DOWN their list. Here's how it works. In the first
round, the programs can offer the same number of positions (for example, the University of Minnesota has six
orthopaedic residents) that they have in their resident class. MN can make six offers to the six top candidates
on their list. Some of the spots will fill, say two of 'em, with people who were top ranked with MN and ranked
MN at the top of their list. There can't be a better fit that, so those spots are out of the match. The other
four spots will be offered DOWN Minnesota's list until they get filled. It doesn't matter if your list is one of the
first run or one of the last. You can't be beat out by a lower ranked candidate. So some of the people
occupying those tentative match spots will be down MN's list until they get to your list. Say you're ranked
highly by MN and you've got them high on your list. You'll be placed tenatively in one of MN's spots and the
process continues until the class is filled with the most desired candidates that ranked that program. If
someone comes along that's more desired by MN than you, and they also ranked MN highly, they'll knock you
down the list. If three other people are more desired by MN and ranked MN highly, they too will knock you
down and off the list (remember, two of the spots were "perfect" matches, i.e., the two top candidates that
MN wants and who want to go to MN). So now you got knocked off MN's list (you won't match there),
because the program is tenatively filled with more desirable candidates (some of whom will get replaced if a
more desirable candidate comes along). So the algorithm looks at your next choice, e.g., Pittsburgh. But, alas,
Pitt didn't even rank you! You can't match there, so it looks at your third choice, e.g., Duke. Duke has you
one their list, but your not one of their top picks. If there are open spots, i.e., the spots are not filled by more
desirable candiates, you tentatively match at Duke until you get moved down and off the list or the Match
runs fully and you're still on Duke's list. In the case of the latter, you've matched at Duke. This process of
checking perople's rank lists and looking to see if they are ranked at that program (and if they are more
desired by that program) continues until everyone is placed with their highest choice that also wanted them,
or the spots are all filled and you're one of the unlucky unmatched candidates. There are two basic strategies
for organizing your rank list. 1. Rank ALL acceptable programs. Orthopaedics, unlike Internal Medicine, doesn't
really allow the option of not ranking programs. Don't rank a program if you absolutely wouldn't want to go
there. 2. Rank the programs in order of YOUR preference. So, if you've got a couple of dream programs that
you'd be thrilled to go to (but maybe don't have the greatest chance), then rank them at the top of your list.
You never know what might just shake out. If your home program is a sure bet and you want to go there,
then rank them first. If your home program (or a few others) are sure bets but you really would like one of
those dream programs, then rank them at the bottom of your list. Remember, you go UP the list. So if they run
the match list of your home program (a sure bet) and it's at the bottom of your list, you can only do better
(never worse). If they run the match list of your home program (the sure bet), and you rank it No. 1, you'll go
there because you can't get a better fit between the two lists. Say you rank the sure thing at the bottom of
the list, they run Sure Bet U's match list, you're on it and they're on your list, you'll be tenatively matched
there. Then when they run some of the other programs that you ranked higher than Sure Bet U, you'll be
tenatively matched at one of those programs and taken off Sure Bet's list. You'll keep moving up YOUR list as
long as there is an open spot at those more desired programs (they offer spots DOWN their list) and you are
more desired than one of the candidates at that program. If these more desired programs are tenatively filled
with more desired candidates than you, you can't take a spot away from those people and you'll end up at
Sure Bet. If Sure Bet U wasn't such a sure bet (you aren't top ranked like you thought and the other programs
either didn't rank you, or you're so far down their lists), you could be knocked off Sure Bet's list by more
desired people. Since there's no place to go down your list, you won't match.
Man, this is a pain to explain. Quick and dirty--1. Rank all acceptable programs. 2. Rank them in the order of
YOUR preference (really want to go to Duke, but don't think you've got much of a chance, then rank them No. 1
or want to go to your home program and they'll almost surely take you, then rank them No. 1) 3. Sure bets (if
you're sure about them) can safely go at the bottom. 4. You accept offers UP your list. 5. Programs make
offers DOWN their list. 6. You can never replace a more desired candidate (you're lower ranked) and, in turn,
you can't be replaced by someone lower ranked than you. 7. The supposed end result is that the programs get
the highest ranked candidates and candidates get their highest choice. Sure hope this rambling exlanation
makes a little sense.
slk
Local user
(6/8/00 8:28:35 am)
Reply
Re: Matching algorithm
Thanks a lot kent, that was a big help. Let me ask you one point of clarification. So if you can never get
bumped off a program's rank list by someone ranked lower than you, does this mean: Say a program ranks me
5 on their list, and I rank them at the bottom of my list, say 15. Someone else is ranked by the program #6,
one below me, but they rank the program No. 1 on their list. Won't that other person be a much better "match"
overall, even though they are ranked a little lower by the program?
Bob
Local user
(6/8/00 9:39:46 am)
Reply
Re: Matching algorithm
A good question.
If you were to rank a program No. 15 (let's say Mayo) and that program ranks you high, let's say #4, then you
would get that spot if you didn't match at one of your higher 14 choices. This holds true even if a student
who ranked Mayo as their top spot and Mayo were to rank them behind you a little bit (say #6). Although it
seems that the other candidate has a better "match", the advantage goes to the student who is ranked higher
on the program's list. I hope that makes sense.
The bottom line is this... when making out your rank list, put the programs in the order that you would be
happiest, and things will work themselves out. Don't try to figure out which programs will be ranking you where
on their list.
Kent
Unregistered User
(6/8/00 1:22:35 pm)
Reply
Paging Dr. Al Gorithm
I think Bob's correct, although I'm far from an expert on this matter. See if you can find some of the articles
written about the algorithm. Let's look at your case. If you are ranked within the number of spots offfered by
the program (say MN has six spots and you're ranked either 6th, 5th, 4th, 3rd, 2nd, or 1st), and you have that
program ranked first, then it's generally a lock that you will go there (you might get picked off by your second
program that had you ranked something like 1st or 2nd). If you are one of the top six at MN, but you ranked
MN last, it would depend on the order in which MN list is run. If MN is one of the first lists run and you're a
top-six pick, then you'll be tenatively placed there. Notice I said "tenative". As they get to the other rank
lists, you might appear sufficiently high on one of your higher ranked program's (say Mayo) list to get moved
UP to that program. So, MN would be the worst you could do. This is why I said that you accept spots UP
your list and programs offer spots DOWN their list. It would seem that you're guaranteed a match somewhere
as long as you're one of the candidates ranked within the total number of the resident class, i.e., six or better
at MN, ten or better at Mayo and Harvard, eight or better at Pittsburgh, etc., etc.). It also would seem to
make sense that unmatched students fall in one of two categories: 1. They weren't ranked by ANY program,
so there can't be a match, or 2. They were ranked, but pretty far down the list (say the algorithm ran their
rank list early on, Mayo's ranked No. 1 and Mayo hadn't tenatively filled with more desired students. This student
is ranked something like 35 on Mayo's list, so there are lots of more desired students to fill a class of 10. Well,
that guy or gal will tenatively occupy a spot until another, more desired applicant's rank list is run and the
latter will move the low-ranked person down a spot or off Mayo's list. Once off Mayo's list, the algorithm looks
at the applicant's next choice and sees if the student can be tenatively placed. If that program has more
desired candidates in the spots, then it's down to the third choice. Maybe the student can be tenatively
placed, but along comes a more desired person, and the lower ranked applicant gets bumped. If this process
continues all the way down this person's rank list (thereby exhausting the list), there aren't any programs left
and the applicant is unmatched. This is what I meant by not worrying about whose rank list gets run first. You
can't be replaced by somebody lower ranked than you and you can't replace anybody higher ranked.
Remember those two simple principles: 1. Rank ALL acceptable programs and 2. Order your rank list according
to YOUR preference, not how you think programs will rank you.
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