Make-or-buy decision
The make-or-buy decision is the choice between producing an input internally and sourcing it from the market.
Every firm is really a bundle of decisions about what to do itself and what to leave to others. The make-or-buy decision is that choice made explicit.
The make-or-buy decision is the choice between producing a good, component, or service in-house and sourcing it from an outside supplier. Repeated across thousands of activities, these decisions define the boundary of the firm: what it owns and does, versus what it leaves to the market.
The market versus the firm
The underlying question is which mechanism organises the activity better. Markets bring competition, specialisation, and flexibility; a supplier under competitive pressure has every reason to be efficient. Doing it in-house brings control, coordination, and protection of sensitive knowledge, at the cost of flexibility and focus. Transaction cost economics frames the trade-off precisely: make when the friction, risk, and hold-up of dealing with the market exceed the inefficiency of doing it yourself.
When buying is dangerous
Buying is usually cheaper and simpler, but not always wise. Outsourcing an activity that is central to the firm's advantage can hollow out the very capability it competes on, handing know-how to a supplier who may later become a rival. Many firms have outsourced their way to short-term savings and long-term dependence, losing the skills they would need to bring the work back.
When making is a trap
Equally, making everything in-house breeds bloat and complacency. Internal suppliers protected from competition drift toward higher cost and lower responsiveness, and the firm accumulates activities it performs worse than specialists would. The instinct to control everything is as dangerous as the instinct to outsource everything.
The sound test separates the strategic from the ordinary. Activities that are central to competitive advantage, or that protect critical knowledge, lean toward make; commodity activities that specialists perform better and cheaper lean toward buy. The mistake firms most regret is outsourcing the first kind to save money on the second.