How did we get so poor?

I was reading about the increasing numbers of America's poor recently. [Source]

In 2005, 37 million Americans were living in poverty. That's over 12% of the total population, or about one in eight. Of those, 16 million (5%, or one in twenty) were in what's considered "deep" or "severe" poverty -- a family of four earning less than $9,903 year.

Considering a minimum wage earner working full time for 52 weeks will get at least $10,900, severe poverty like this can only be attributed to lost jobs. Concentrated along the Mexican border and in some areas of the South, severe poverty is the result of manufacturing industries disappearing. Naturally, single wage-earning families are the hardest hit .

The promise of supply-side economics is that by cutting taxes on the rich, investment in U.S. businesses will go up, and the number of jobs will follow.

But with supply-side economics having been both theoretically invalidated by a 2003 government report, and practically invalidated by the growing ranks of jobless poor, I wonder how politicians will change the tax-cut-based policies that have characterized the past 7 years?