A few ideas:

• once people start with C and have understood how to use *ptr and **ptr and ***ptr and worse... productivenss increases a lot, because there are literally no boundaries from the language: any hack is possible, including abusing syntax sugars
• once people realize that they don't understand shit of their own code 2 days later, they start trying to figure out how to write maintainable C... from that point on, productiveness almost constantly goes down while safe-assessment goes up (because you understand all the random pitfalls that can happen)

However, you could argue that most people never even try to write maintainable C code and get to a completely different conclusion... discovering more hacks every year and lose more sanity every year.

Another thing to consider is what we actually mean with productiveness: shortterm or longterm?

http://elm-lang.org/learn/What-is-FRP.elm
:(

Said chart as far as it goes is correct, but to capture more than the infancy of the Javascript developer it fails. That callbacks are hell it is truly said, but marshaling of asynchronous execution to success in modern Javascript is key, and for that reason the successful Javascript developer eventually discovers futures, which in this context most commonly by the name promises are known. At this point most often another reversal occurs.

XD Ugh, not to be that guy but...
For functional_programming_in_cpp_with_the_functionalplus_library_today_hackerrank_challange_gemstones.md

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English, at least as she is in America spoke, generally uses the term "self-assessment" to refer to what is at least intended to be a relatively objective analysis of one's capabilities, which is often produced in the context of employment, eventually written down on paper, and retained in an employee's permanent file.

Having twice now read your learning-curves article, I tend to suspect that the quality which, in the charts, you name "self-assessment", might more fluently in English be named something like "self-opinion", or perhaps ideally "self-regard"; this would, I think, make a lot of the charts easier on first reading to understand. (For example, interpreting in this fashion your PHP chart, one might gather that PHP programmers have an unjustifiably high regard for themselves, which would most in line with your intent seem to be.)

Just wanted to share that I really enjoyed reading:

https://github.com/Dobiasd/articles/blob/master/from_oop_to_fp_-_inheritance_and_the_expression_problem.md

Feel free to close issue!