Stock vs Flow

In economics, a ‘stock’ is a measurement taken at a specific point in time. A ‘flow’ is measured over a particular interval. Stocks are measured in units – pounds sterling, number of attendees, kilometers. Flows are measured in units/time – salary per annum, sales per month, or kilometers per hour.

Stocks and flows can tell very different stories. For example, a business with lots of sales and lots of expenses may have a high weekly revenue (flow), but very little cash on hand (stock).

How does this relate to migration?

How many migrants are there?