Don Brunell

It’s often difficult to “connect the dots,” to show people how the global marketplace affects their daily lives. But plunging gasoline prices are giving Americans a first-hand lesson in the law of supply and demand.

The law of supply and demand holds that when a commodity is in short supply, the price of that commodity goes up. When the supply of that commodity increases, producers compete for market share by lowering their prices. As a result, consumers benefit.

That’s what happening with gas prices. The price of gasoline has been dropping steadily over the summer, down to less than $3 a gall...