Does anybody know where one can find a study on the price distribution of a commodity at time B as a function of time a (time B > time A)? Essential I'm trying to find the probability density function of Rho, where Rho is defined as Rho(Time B - Time A) = Price(Time B) - Price(Time A). My thought is that for somewhat short time periods, price movements are random and symmetrical. If this is the case, one might be able to open a position at Time A. One could limit the downside of this position by placing a stop-loss. If the stop-loss isn't reached by Time B, then one automatically closes his/her position. Over time, this system would surely make profits, so long as the probability of the price reaching the stop loss and then returning to profitibility within the alloted time isn't very high. If we assume that the width of Rho decreases with decreasing time, and we assume it takes some finite period of time to reach the stop loss, it seems to me that this system would work. I'm going to test this system for a few months and see what happens.