A few months ago I proposed writing a book that would answer all your questions in detail, but there wasn't enough interest to make it worth doing. There are many good books out there already that address these issues. I get that "Dummies" books are too low-status for you. I'll try to dig up some equally well-written, correct references that are higher status and explain things like "what an index fund is?" "what's a reasonably long time horizon?", and "what other investments are possible?" For starters, I've heard good things about Suze Orman's books, though I haven't read them myself.
Your formulation of the weak efficient market hypothesis is incorrect. The weak EMH is not based solely on past prices, but on all publicly available information.
are too low-status for you
No, it's not an issue of status. They are too simplified and do not reflect reality to the degree that I consider necessary. It's like telling a competitive athlete "Oh, physical fitness is solved, just go to the gym".
I don't want references, anyway. You are claiming that investing is solved. You are saying that the only correct investment is into an index fund. Well then, tell me what's an index fund. Is it just any passive diversified investment? There are a great many indices, are all of them equally good? How div...
Follow-up to: Boring Advice Repository
Many practical problems in instrumental rationality appear to be wide open. Two I've been annoyed by recently are "what should I eat?" and "how should I exercise?" However, some appear to be more or less solved. For example, various mnemonic techniques like memory palaces, along with spaced repetition, seem to more or less solve the problem of memorization.
I would like people to use this thread to post other examples of solved problems in instrumental rationality. I'm pretty sure you all collectively know good examples; there's a comment I can't find from a user who said something like "taking a flattering photograph of yourself is a solved problem," and it's likely that there are other useful examples like this that aren't common knowledge. Err on the side of posting solutions which may not be universal but are still likely to be helpful to many people.
(This thread is allowed to not be boring! Go wild!)