A way of measuring overnight activity in the futures market by just noting how much of the overnight activity happens to fall above the prior day’s settlement value (4:15pm EST close) and how much falls below. If more activity is above the settlement, then overnight inventory is said to be net long. If more is below, then it is said to be net short. If all of the overnight activity is above the settlement, then it is said to be 100% net long. If all of the activity is below the settlement then it is said to be 100% net short. The overnight inventory situation matters most and has the most impact on early trade when it is skewed 100% in either direction because when the imbalance is very large like that then the odds of an early correction increase greatly. This is due to the fact that most overnight traders are weaker hands and emotionally driven. If the RTH activity right after the bell doesn’t confirm their overnight bias, they will usually reverse their positions quickly.