&gt; At the very least that data does not really fit the theory.<p>What theory? It certainly fits <i>a</i> theory: that insecurity (and, thus, plenty of <i>downward</i> mobility), limited upward mobility, and a steep drop to the bottom combine to provide a condition in which members of the <i>middle</i> class become more prone to reject the existing social order and adopt extreme alternatives that are offered.