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

What does it mean that stocks are “memoryless”?
With my current, limited knowledge (see end), I understand it the following way: Are share prices really described as "memoryless"?  Yes.  Is there a   technical meaning of the term? What does it really mean? The meaning comes from Markov Models: Think of the behavior of the stock market over time as a Markov Chain, i.e. a probabilistic model with states and probabilistic transitions. A state is the current price of all stocks of the market, a transition is a step in time. Memoryless means that transitions that the stock market might make can be modelled by a relation from one state to another, i.e. it only depends on the current state. The model is a Markov Chain, as opposed to a more general Stochastic Process where the next state depends on more than the current state. So in a Markov Chain, all the history of one stock is "encoded" already in its current price (more precisely in all stock's prices).  The memorylessness of stocks is the main statement of the Efficient Market Theory (EMT). If a company's circumstances don't change, then a drop in its share price is going to be followed by a rise later.  So if the EMT holds, your statement above is not necessarily true. I personally belief the EMT is a good approximation - only large corporations (e.g. Renaissance Technologies) have enough ressources (hundreds of mathematicians, billions of $) to be able to leverage tiny non-random movements that stem from a not completely random, mostly chaotic market.  The prices can of course change when the company's circumstances change, but they aren't "memoryless" either. A company's future state is influenced by its past. In the EMT, a stock's future state is only influenced by its past as much as is encoded in its current price (more precisely, the complete market's current state). Whether that price was reached by a drop or a rise makes no difference.  The above is my believe, but I'm by far no finance expert. I am working professionally with probabilistic models, but have only read one book on finance: Kommer's "Souverän investieren mit Indexfonds und ETFs". It's supposed to contain many statements of Malkiel's "A Random Walk Down Wall Street".