Time arbitrage is exchanging time at one value for time at a higher one. It is the practical mechanism behind most changes in how much a person earns.

The basic trade

Hiring is the obvious case. If your time produces $200 an hour and you pay someone $40 to do work you were doing, you have bought back hours at a fifth of what they produce. The gain is the spread, and it only exists if you actually use the freed hours on higher-value work rather than on more of the same.

That condition is where the trade usually fails. Buying back ten hours and spending them on tasks worth $40 converts a good trade into a wash plus a management overhead.

The other direction

Time arbitrage also runs forward. Building something today that produces for years exchanges present time at today's rate for future time at a much higher one. A documented process, an article, a piece of software — each costs hours now and returns them repeatedly. See leverage and compounding.

It runs across contexts too. The same skill earns very different amounts depending on who is buying it, which is why the largest single income change most people make is a change of buyer rather than an improvement in capability. See career capital.

Working out your own number

Take what you want to earn annually, divide by roughly two thousand working hours, and you have an hourly figure. Any task available for less than that figure is a candidate to buy out, and the decision is arithmetic rather than a question of whether you can afford help.

Most people refuse the trade because the saving is visible and the gain is not. Paying $40 shows up on a statement; the $200 of work it enabled does not show up anywhere, so the decision reads as a cost. See hidden cost.

The limit

The trade requires demand for your higher-value hours. Buying back time with no pipeline waiting for it produces free time and a bill, which is why this works better as a response to being constrained than as a way to create capacity you have no use for.

What makes the trade sound rather than merely appealing is comparative advantage. Buying an hour for less than your hour produces is a gain even when you are better at the task than the person you bought it from — being better at something was never the argument for doing it. The spread is the whole mechanism, and it survives being worse at nothing.