Machine Learning (Theory)


Not goal metrics

Tags: General jl@ 9:10 am

One of the confusing things about research is that progress is very hard to measure. One of the consequences of being in a hard-to-measure environment is that the wrong things are often measured.

  1. Lines of Code The classical example of this phenomenon is the old lines-of-code-produced metric for programming. It is easy to imagine systems for producing many lines of code with very little work that accomplish very little.
  2. Paper count In academia, a “paper count” is an analog of “lines of code”, and it suffers from the same failure modes. The obvious failure mode here is that we end up with a large number of uninteresting papers since people end up spending a lot of time optimizing this metric.
  3. Complexity Another metric, is “complexity” (in the eye of a reviewer) of a paper. There is a common temptation to make a method appear more complex than it is in order for reviewers to judge it worthy of publication. The failure mode here is unclean thinking. Simple effective methods are often overlooked in favor of complex relatively ineffective methods. This is simply wrong for any field. (Discussion at Lance‘s blog.)
  4. Acceptance Rate “Acceptance rate” is the number of papers accepted/number of papers submitted. A low acceptance rate is often considered desirable for a conference. But:
    1. It’s easy to skew an acceptance rate by adding (or inviting) many weak or bogus papers.
    2. It’s very difficult to judge what, exactly, is good work in the long term. Consequently, a low acceptance rate can retard progress by simply raising the bar too high for what turns out to be a good idea when it is more fully developed. (Consider the limit where only one paper is accepted per year…)
    3. Accept/reject decisions can become more “political” and less about judging the merits of a paper/idea. With a low acceptance ratio, a strong objection by any one of several reviewers might torpedo a paper. The consequence of this is that papers become noncontroversial with a tendency towards incremental improvements.
    4. A low acceptance rate tends to spawn a multiplicity of conferences in one area. There is a strong multiplicity of learning-related conferences.

    (see also How to increase the acceptance ratios at top conferences?)

  5. Citation count Counting citations is somewhat better than counting papers because it is some evidence that an idea is actually useful. This has been particularly aided by automated citation counting systems like and However, there are difficulties—citation counts can be optimized using self-citation and “societies of mutual admiration” (groups of people who agree implicitly or explicitly to cite each other). Citations are also sometimes negative of the form “here we fix bad idea X”.
  6. See also the Academic Mechanism Design post for other ideas.

These metrics do have some meaning. A programmer who writes no lines of code isn’t very good. An academic who produces no papers isn’t very good. A conference that doesn’t aid information filtration isn’t helpful. Hard problems often require complex solutions. Important papers are often cited.

Nevertheless, optimizing these metrics is not beneficial for a field of research. In thinking about this, we must clearly differentiate 1) what is good for a field of research (solving important problems) and 2) what is good for individual researchers (getting jobs). The essential point here is that there is a disparity.

Any individual in academia cannot avoid being judged by these metrics. Attempts by an individual or a small group of individuals to ignore these metrics is unlikely to change the system (and likely to result in the individual or small group being judged badly).

I don’t believe there is an easy fix to this problem. The best we can hope for is incremental progress which takes the form of the leadership in the academic community introducing new, saner metrics. This is a difficult thing, particularly because any academic leader must have succeeded in the old system. Nevertheless, it must happen if academic-style research is to flourish.

In the spirit of being constructive, I’ll make one proposal which may address the “complexity” problem: judge the importance of a piece of work independent of the method. For a conference paper this might be done by changing the review process to have one “technical reviewer” and several “importance reviewers” rather than 3 or 4 reviewers. The “importance reviewer” is easier than the current standard: they must simply understand the problem being solved and rate how important this problem is. The technical reviewers job is harder than the current standard: they must verify that all claims of solution to the problem are met. Overall, the amount of work by reviewers would stay constant, and perhaps we would avoid the preference for complex solutions.

One Comments to “Not goal metrics”
  1. […] It seems reasonable to cross reference these options with some measures of ‘conference impact’. For each of these, it’s important to realize these are not goal metrics and so their meaning is unclear. The best that can be said is that it is not bad to do well. Also keep in mind that measurements of “impact” are inherently “trailing indicators” which are not necessarily relevant to the way the conference is currently run. […]

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