"Even a small productivity gain (say 5%) over a long period of time can make a very large difference, and is worth spending weeks to learn."
The question then raised is whether any given new programming language or paradigm will bring that 5% productivity gain, and in what circumstances. If it were an obvious and clear path to greater productivity, and superior to other paths to greater productivity (such as spending more time learning your editor and shell and environment, or learning about a new library in the language your work is written in, or learning new tricks in your current language), no one would hesitate to increase their productivity in this way.
You seem to assume that people are choosing not to become more productive by opting not to switch to Haskell or learn Haskell or something about Haskell. There are thousands of programming languages. Shall we learn them all to become five thousand percent more productive?
I'm not opposed to learning new languages. I think folks should tinker. But, I don't think it is provable that learning Haskell will make you more productive than other activities.
The question then raised is whether any given new programming language or paradigm will bring that 5% productivity gain, and in what circumstances. If it were an obvious and clear path to greater productivity, and superior to other paths to greater productivity (such as spending more time learning your editor and shell and environment, or learning about a new library in the language your work is written in, or learning new tricks in your current language), no one would hesitate to increase their productivity in this way.
You seem to assume that people are choosing not to become more productive by opting not to switch to Haskell or learn Haskell or something about Haskell. There are thousands of programming languages. Shall we learn them all to become five thousand percent more productive?
I'm not opposed to learning new languages. I think folks should tinker. But, I don't think it is provable that learning Haskell will make you more productive than other activities.