Why this is mistaken
Gross productivity answers who can produce more with a common input. It does not answer who gives up less of another output to produce one unit.
Require a two-stage worksheet. Mark absolute advantage from direct output comparisons. Then compute each producer's opportunity cost in both directions and mark comparative advantage from the lower sacrifice. The results may assign different labels to the same producer.
The diagnosis is complete only when you can explain how a producer with lower output in both activities can still have lower opportunity cost in one. Do not proceed to trade terms until units and reciprocals reconcile.
Where to watch
When this mistake may appear
- One producer can make more of both outputs.
- A prompt asks who should specialize rather than who is more productive.
Check your work
Your work may contain this mistake if:
- Assigns both activities to the producer with absolute advantage in both.
- Compares output levels but never computes reciprocal opportunity costs.
- Says a less productive party has nothing to contribute to exchange.