What important economic indicator declined in the late 1920s?

What is a social-conflict theorist looking for when studying the labor market? When does the economy get bad? Is a shopping mall a public good? Is the long-run aggregate supply curve upward sloping? What kind of elastic demand does electricity belong? What economic and cultural activities took place in Cordoba? You want disadvantages of ecological farming? What are emotional intelligence of Martha Stewart? What was the Dow Jones at on Jan 1 2013? How is economics often described? How do you value oil reserves? Which economist opposed protectionism the policy of a nation imposing taxes on imported goods? How does the Engel curve for inferior goods illustrate the relationship between income and consumption patterns? What refers to the process of manufacturiing that introduced powered machinery to the production of goods? Can Productivity gains curb inflation? Importance of valuation? How do we calculate IS equilibrium of national income? What factors contribute to an increase in demand for a good? What country was developed an important school of navigation in the 1400? What is the value of a 1998 US 2 dollar bill?