This is an interesting read, would be interested if DUers agree...
Nate Silver
1/5/09When the House of Representatives convenes tomorrow, it will contain 39 African-American members, not including non-voting delegates in places like the Virgin Islands and the District of Columbia. This number, representing about 9 percent of the Congress, falls somewhat short of the fraction of African-Americans in the population as a whole -- a truly representative House would have about 55 black members -- but perhaps not dramatically so. The situation at first glance would appear to be much better than it was prior to 1990, when there were generally only about 20 black members in the House at any given time.
The districts these 39 Congressmen serve, however, are not very representative at all. All 39 contain a higher percentage of African-Americans than the population as a whole, ranging from Keith Ellison's district in Minneapolis, which is just barely more black than the national average, to Jesse Jackson Jr.'s on the South Side of Chicago, which is 68 percent African-American. About 64 percent of the members -- 25 of 39 -- come from districts that contain an outright black majority. The districts are also much more Democratic than the country as a whole, with an average PVI of D +25; only Sanford Bishop's district in Georgia, which has a PVI of D+2, is anywhere close to the national average.
The chart below estimates the percentage chance that the Representative in a given Congressional District is black given the African-American population in that district, as based on a logistic regression. The chances of having a black Representative are virtually nil until the African-American share of the population hits 25 percent, at which time it begins to accelerate rapidly until the black population hits 60 percent, after which point having a black congressman is virtually certain.
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If one looks at the composition of the House of Representatives, then, one shouldn't be surprised that there are so few black senators and black governors, because states are far more heterogeneous (racially and otherwise) than individual Congressional Districts, and African-Americans are by and large not getting elected to the House outside of a certain number of highly black, largely homogeneous, and often heavily gerrymandered Congressional Districts in the urban North and the rural South.
The question, of course, is why African-Americans aren't getting elected in these districts. Racism is undoubtedly part of the answer, but it probably can't be a complete one now that the country has just elected Barack Obama to the White House.
more:
http://www.fivethirtyeight.com/2009/01/why-are-there-no-black-senators.html