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Fluency Percentage is not consistent

I've noticed that the fluency percentage badge never stays at one percentage for very long. And I'm not talking days, I'm talking minutes.

For the past few days, I've been bouncing between 49% and 50% in French. Every time I strengthen a skill, the percentage bounces up to 50%, but then a few minutes later it drops back down to 49%. I can't tell if it's a glitch or if the calculator was just poorly programmed. Is anyone else having this problem?

June 1, 2015



Fluency is calculated as a value between 0 and 1. For example, for you it's 0.4956215294. This is then multiplied by 100 and rounded off to the integer part to show the fluency. So, in your case the fluency is actually 49.56% though you see 49%. While it's actually just a drop of less than 0.0044 from when you had a value of 50%, this shows up as a drop of 1%.


First, that would imply a floating point precision of only 1 digit. Even the smallest floating point number has higher precision than that.

Second, my percentage goes up AND down constantly. It's not just two numbers going back and forth. I get 50, 51, 52, and 53. It is simply not possible for round off errors to explain this bug, unless the feature was implemented in a VERY stupid way.

In any case, it needs to be fixed, it's SUPER terrible for a user's level to go up and down by multiple percent each day.


In any case, it needs to be fixed, it's SUPER terrible for a user's level to go up and down by multiple percent each day.

Its a computer generated guide, not a definitive measure of your fluency. What is so terrible that it varies a bit now and then? It really is not the end of the world you know. I have just started the reverse Italian course i.e English from Italian. I am a native English speaker with a C2 fluency level in English but my Duo's fluency measure is 17%, it is just a rough guide, don't get upset because it is not accurate to the 100th decimal place.


It's not a measure of fluency at all. I mean, nobody here actually believes they will be "fluent" in a language when that number reaches 100%, do they? No. The shield is a gamification feature. Just like your "level" and your 501-day streak. (Nice one btw!)

Just as it would not be okay for our levels to randomly go up and down and our streaks to randomly break, gamification features should not be unpredictable.

As a game developer, I am VERY confident that having broken game features like this is MUCH worse than not having them at all.

In any case, even if it really is just a "guide", it's obviously very broken if I lose 2% of my fluency by completing a new course. It makes no sense.


Of course it is a measure of fluency, just not a very good one.

Duo seem to test all new functions to ensure that they improve the learning experience so presumably they will remove it if it fails that test.


Well, I AM fluent in Portuguese and my fluency according to Duo is 52% (and I got all the answers right on the test ;) ) My Danish fluency is totally crazy, different every time I complete a task. It would be nice if the fluency tool was fixed, it's a bit demotivating as it is now. Seems like a totally useless device.


I am not sure that's an error. The movement up or down happens as per Duolingo's algotithm. They may still be fine-tuning it but it will always behave in similar way. The value they identify will be based on a list of parameters and these will not be static. At a very high level, we can probably directly co-relate it with the words' strength. When already learnt words decay, that push down fluency. Thus revising old words helps bump it up. Similarly, adding more new words would help to bring up the value.

In any case, it needs to be fixed, it's SUPER terrible for a user's level to go up and down by multiple percent each day.

Actually, my percentage hasn't changed much since I got the value. It was 58 when the fluency value got added. After completing a bunch of new lessons, it had gone upto 59. But then it's back to 58 and has stayed the same for more than a week. At 0.5838173239, I don't expect it to fall anytime soon. For it to rise, I will probably need to put in a good amount of revision.


I lose 2% of my "fluency" by completing a new course and that's not an error? Come on. It's super buggy.


If you want to keep a track of it, try maintaining a spreadsheet of the words in your Words tab which are not at full strength. Probably, you should be able to find a direct co-relation between that number and the fluency score.

There may be many other parameters as well of which only Duolingo will be aware.


> Actually, my percentage hasn't changed much since I got the value.

Huh. Mine has. It bobs around like a spastic buoy.


Yes, constantly. Been having it for weeks.


i am at 49% too. how ever mine is by 3-7 days


I don't have a fluency percentage... where do you see that?


It's currently being tested with only a part of the users able to see the score.


Some specific data in case Duo developers actually read this:

  • my percentage today was at 52 when I first started.
  • I completed a timed practice and it was still at 52.
  • I closed the page and opened it a few minutes later and it was at 53.
  • I completed another timed practice and it immediately went to 51.
  • I did another timed practice and bombed out -- got 0 correct, and it was back up at 53.


In general, after you first open to the webpage, then complete your first exercise, go back to home page (that's where the fluency badge is, correct?) and refresh the page. And you essentially did that when, at 52, you did your exercise then closed and reopened to the 53. I'm wondering: after that 1st timed practice that you got 51, then on 2nd timed prac saw 53, did you do those last 2 timeds on tabbed pages or new windows that were separate from the page when you reopened at 53? In other words, are you switching between pages when doing exercises? Originally opened unrefreshed pages will still reflect previous info.


No, I only use one tab for Duolingo. (I only ever use a few tabs at a time.)

There's definitely something being cached weirdly, but it's not in the browser -- I've gotten into the habit of refreshing the page to see if that will change the percentage, and it never does. Recently I've been closing the browser and reopening it to clear any temporary cookies, but that doesn't do anything either. However, closing it and reopening an hour later does sometimes show a different value.


Gotcha. This is a subject that definitely needs more follow up and explanation. This issue and the constant dropping of the ratings on the tree exercises seem to be a persistent befuddlement to Duolingoers across the discussion boards.


I just noticed the same thing tonight.

  • 2227

In the past month, after doing 50+ points per day, several translations, and 're-golding" my entire tree, my fluency rating has fluctuated between 57 and 58 percent. It has hardly varied. It seems that what I do has little or no effect on it. To add insult to injury, I can begin my daily exercises with a 58, do 50 points, and end with a 57.... Now that's punishment ha ha.

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