The 5 and 20 numbers are arbitrary, but they are almost exactly equidistant from the national black population of 12.8% (US census, 2006). I wonder if the dividing lines are actually closer to the national average or further apart.
With that in mind, here's the black population of upcoming primary/caucus states:
LOUISIANA: 31.7%
NEB: 4.4%
WASH state: 3.6%
MAINE: 0.8%
DC: 56.5%
MD: 29.5%
VA: 19.9%
HAWAII: 2.5%
WISCONSIN: 6.0%
OHIO: 12.0%
RI: 6.3%
TX: 11.9%
VERMONT: 0.7%
WY: 0.9%
MISSISSIPPI: 37.1%
PA: 10.7%
IND: 8.9%
NC: 21.7%
WV: 3.3%
KENTUCKY: 7.5%
OR: 1.9%
MONTANA: 0.4%
SD: 0.9%
http://quickfacts.census.gov/qfd/states/22000.htmlhttp://politics.nytimes.com/election-guide/2008/primaries/democraticprimaries/index.htmlThese numbers are, of course, the percentage of overall state population. Undoubtedly the vast majority are registered Dems, so the percentage of the Dem voters might be nearly twice as high.
This theory almost completely coincides with my own personal intuition of which states should be favorable for Obama and which would favor Hillary. Without really knowing the black population, or the theory of the OP, it seemed Ohio, Texas, and PA are the strongest for Hillary--they also happened to be almost exactly at the national average of 12.8%. Virginia and Wisconsin seemed possible for Hillary--and they are right at the edges of the OP theory.
K&R.