Market moves are generally seen as independent from one another. Although that is true for small moves (less than 1% in magnitude), larger moves tend to not be independent.

In other words, if a large move (greater than 2% in magnitude) is observed on any given day, there is a greater chance to see another large move tomorrow than the chance of seeing a large move on any given market day.

In fact, if we have a 5% move today, it is 37 times more likely to see another 5% move the next day than a 5% move on any given market day.