So the general consensus is that the traders will return from vacation on Tuesday and volume will come back. But does volume always return after Labor Day? What if it doesn’t? I studied it tonight:

The study above suggests negative consequences should Tuesday’s volume not surpass Friday’s. The sample size is quite small, though and there have been no occurrences since 1994. Therefore I decided to widen the parameters. In this case I’m looking for instances where post Labor Day Tuesday volume doesn’t manage to exceed all of the days the previous week.

More instances. Similar results. The bulls should hope traders make a quick return from vacation Tuesday. Otherwise, September could be a difficult month.