Thanks for the upvote!
As I mentioned in my comment, this is definitely economics. One of the foundational questions in economics is the determination of prices in equilibrium. The CAPM is a model of how prices of durable goods (capital) are formed in market equilibrium.
The intersection of finance and economics
To note, there is a lot of recent research in economics that is trying to connect real markets with financial markets. This research is seen to be extremely important right now. Also, there is a lot of research in finance that incorporates economic tools. For example, people incorporate economics to study the incentive structure on corporate executives. This is also important within the intersection of applied micro and finance. Questions along these lines should definitely be included. As you guys mentioned, I would favor more inclusiveness.
For the most part, I would go so far as to say that finance is a sub-field of economics. (It's also worth noting that a large percentage of top finance professors got their PhD's in economics.)
Rules for inclusion
Maybe some of these could be guidelines.
- As a general guideline, if it could be argued that the question is on topic in an economics class, then it should belong here. (As an example, notice the number of economics classes here that are about finance. There's about 10.)
- Also, it might be nice to suggest to people
quant.stackexchange.com. But, if people are aware of
quant.stackexchange.com and still choose to put the question here, then maybe we should give them the benefit of the doubt (as a rule) and let them post the question here (assuming it's not a cross-site duplicate). It might be better to err on the side of inclusiveness.
- But, yeah, it's hard to say which questions. But questions on
quant.stackexchange.com are usually more computationally focused and usually deal more with the measurement and prediction. Questions that belong here should be more about the theories and the econometric testing of those theories---economics/financial theories of how the work works. (Although measurement is an important topic---it could still appear here. It's just hard write a hard and fast rule---maybe there shouldn't be one...)
Example of a Quantitate Economics question
ZSpread in multiple curve framework. how do I calculate ZSpread for a govt. bond in a multiple curve framework? I have not come across the exact details anywhere so I want to verify if I'm right...
I think the linked question is a perfect example of a finance question that definitely belongs on
When Markowitz went to publish his economics PhD thesis at the University of Chicago, Milton Friedman rejected it saying that it wasn't economics. Markowitz eventually got it through and the work that he did in his thesis later became a cornerstone of his winning of the Nobel prize in economics.