This trend is tied to a variety of factors. I think that the most important factor is the profit motive in the U.S. and increased practice of outsourcing. Companies are cutting costs by outsourcing non-core tasks or production to overseas facilities. The residual profit is distributed to shareholders and top managers and executives as incentives for increasing profit. There is a huge drive for pay for performance incentives in the U.S. This half of the equation helps managers increase shareholder value and contributes to higher income for the top 1%.

At the same time this decreases the number of middle income jobs available in the U.S. and lowers middle income wages because of lower demand for skills and a higher supply of unemployed workers. This decreases the size of the middle class as well. Imagine the disparity as this trend continues in the future.

Unfortunately this will enter the political arena in favor of liberals, understandably so. In a society in which the majority and vote/legislate itself entitlements (the government provide prosperity) by taxing the more fortunate, there will be a movement to decrease the income disparity by taxation and redistribution.

I think that the world economy is doing great. The U.S. economy is on a trail to depletion.

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"Democracy is a process by which the people are free to choose the man who will get the blame."

-Laurence J. Peter