Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How to calculate how much a large stock position is really worth?
This is actually a very complicated question. The key reading in this area is a seminal paper by Almgren & Chriss, "Optimal Execution of Portfolio Transactions" (2000). They show that there's a tradeoff between liquidating your portfolio faster and knowing the value with more certainty, versus liquidating more slowly (and likely for a higher price) but with less certainty. So for example, if you sold your entire position right now, you would know almost certainly how much you would get for the position. Or, you could sell off your position more slowly, and likely get more money, but you would have less certainty about how much you would get. The paper is available online at http://www.courant.nyu.edu/~almgren/papers/optliq.pdf