Path dependency happens when current events interfere with future events. There are two extreme models of path dependency.

Imagine you have an urn full of white and black balls and you get to draw one at random from the urn.

If, after drawing a ball, you get to add two balls of the same colour drawn back into the urn before you draw again, you end up with the Polya process. The Polya process models the situation where anything can happen. After drawing 1000 balls, the probability that the urn contains 40% white balls is the same as the probability that it contains 5% balls. Interestly, a Polya process should not be confused with a tipping point as the entropy of the process decreases gradually even if the same coloured balls keeps getting drawn.

If the rules are changed such that after drawing a ball from the urn, you introduce two balls of