An interesting column in the Wall Street Journal discusses how American ethnic groups whose members relied on individual effort to advance themselves (e.g., Germans and Asians) advanced much more quickly than those who relied on politics (e.g., Irish and Blacks). I’d like to see more data points than the author provides, but his thesis is certainly plausible.
POSTSCRIPT: For some reason, the direct link doesn’t seem to work, but this Google link does, for now anyway.