The threat of protectionism.

The accelerating freefall of the global economy in recent months has led to talk that we might be headed for a repeat of the Great Depression of the 1930s. The dynamics that led to that dark period in U.S. history, and how the shipping industry was and is impacted by market cycles are the topics of discussion in a new edition of a book, "Maritime Economics," by Martin Stopford, head of Clarkson Research.

Then, as now, government subsidies and bailouts were widely being used in attempts to stimulate sagging economies. In 1929, Britain was the world maritime superpower, but its share of the world fleet had shrunk in the previous decade from more than 40 percent to 30 percent. In 1920, the U.S. Congress passed the Smoot-Hawley Act in an attempt to jump start manufacturing by raising tariffs on 20,000 imported goods. The result was a 50 percent reduction in trans-Atlantic trade during the next two years, which many credit as the final push into the Great Depression.

For the shipping industry, this meant plunging freight rates, ships laid up and fire sale prices on foreclosed vessels. Sound familiar?

Today's version of Smoot-Hawley pending in Congress is the "Buy American" bill in the House and Senate. The House version mandates domestic iron and steel be used for ...