Stocks vs Flows : How Long Do Students Remain in School?

The question in the title is intentionally ambiguous. Whom are we interested in--entering students or those already enrolled? The length-of-stay distributions for these two groups will rarely be identical. Social scientists carefully distinguish between stocks and flows. A stock describes items in a given place at a fixed point in time. A flow denotes the movement of items past a given place over time. This note is designed to illuminate the difference between the duration of stock versus flow items.