1. Practical economists know their likes & dislikes and act accordingly.

They have good information about what makes them happy -- and behave rationally.

2. Practical economists try to maximize their satisfaction.

They behave rationally.

3. They respond to incentives.

They behave rationally.

4. They decide if the extra benefits exceed the extra costs of doing something.

They make their decisions at the margin.They behave rationally.