If you want to know the state of the economy, look no further than Detroit and its automakers. After all, the economy is based on the flow of goods and services, and it's transportation that enables those flows. The more things move, the higher demand there is for the cars and trucks that move them.

What's more, manufacturers of the metals, glass and plastics that go into vehicles, as well as workers who build highways, upkeep roads and repair cars, all depend on the economic strength of the auto industry.  The Alliance of Automobile Manufacturers estimates that every job the auto industry creates equals nine supplier or downstream jobs – that impact alone is pretty powerful.

The good news is that things are looking up for Detroit. U.S. auto sales are predicted to gain 10 percent for a third straight year.  That figure might not mean much to those outside the industry or Wall Street, but to put it in perspective, such a streak has occurred only four times since the Great Depression.

Beyond serving as a barometer for the general economy, Detroit also represents the composition of it. The types of vehicles being made, the processes used to make them and the attributes people consider in their purchasing decisions – each provides insight into the general direction of manufacturing and consumer sentiment in our country.