Let the People Define the Regions
Michael Cain
This off-the-cuff piece is inspired by,
in order,
people here saying
"When you write about X, it sounds like a foreign country,"
for values of X like the South, the Midwest, or the Northeast;
James Hanley's
definition of the Midwest
and the amazing set of "But wait!" comments it got;
and Mike Schilling's (entirely proper) insistance that mathematics is a part of being well-rounded.
I have occasionally floated the hypothesis that
multi-state regions can are defined by
the pattern of migration between states —
on the theory that people generally prefer to move within a region where they are comfortable.
My thought was originally spurred by playing with
this nifty visualization tool.
The Census Bureau provides summary spreadsheets for state-to-state migration flows
here.
Caveats if you're going to play with them:
the 2009 data is in a different layout than 2011 and 2012, and
the 2010 file is corrupted in some fashion and won't open.
You might also enjoy fooling with
Forbes' county-level interactive application
based on IRS data.
With an appropriate distance measure defined based on
the number of people that move between states [1],
it's possible to partition the states into clusters such that
states within a cluster are all "close" to one another and
not so close to states in other clusters.
I used a heirarchical partitioning scheme that builds clusters
from the bottom up,
using the average distance between cluster members
to decide which clusters to merge.
The seven-region shown here even makes some sense:
there's a Northeast,
a West,
a Midwest split in two parts,
a Southeast,
a Mid-Atlantic, and
a "Greater Texas" group.
To James' definition of the Midwest,
migration patterns say Kentucky should be included with Illinois, Indiana, and Ohio;
Kansas and Missouri are Texas-centric,
not Midwestern.
[1]
Which pairs of states are closest by this measure?
Minnesota/North Dakota,
California/Nevada,
Massachusetts/New Hampshire,
Colorado/Wyoming, and
Kansas/Missouri
are the five closest pairs.
This generally coincides with our —
or at least
my —
intuition about things.