"The Ten Limerick Principles of Economics"

A fun and racy look at the principles of economics through limericks - here are numbers 2 and 8 (limericksecon.com via Greg Mankiw):

 #2. The Cost of Something is What You Give Up to Get It."Never free are the amorous fruits,"
Said a girl who astutely computes,
"For there's much I'd have earned
If these calories burned
Had involved more productive pursuits."

Decision-makers have to consider both the obvious and implicit costs of their actions. 

#8. A Country's Standard of Living Depends on Its Ability to Produce Goods and Services.
"My sweet," said a lovable lout,
"Of this there can be little doubt:
The continuing health
Of our national wealth
Is dependent on how you put out."

Countries whose workers produce a large quantity of goods and services per unit of time enjoy a high standard of living. Similarly, as a nation's productivity grows, so does its average income.