State Legislature District Growth from 2000-10

The demographics of U.S. legislative districts are easy to find, and they will always interest me.  The most basic demographic data point is district headcount.  Districts begin the decade with equal population, but population grows and shifts significantly in a short period of time.

How much variation do we see?  Quite a bit, and in recent years, growth skews strongly in the direction of districts represented by Republicans.  The trend isn’t surprising, and it conforms to population growth trends that are more general (e.g., Texas is growing rapidly, the northeast isn’t growing very much, though more than you might suppose).  Keep in mind that the population grew from 281 million to 308 in 2010, and 320 million at the start of 2015.

For the 2000-2010 decade, this graph shows the distributions of population growth for Democratic and Republican state lower house legislative districts as of 2012, the last year that 2000’s redistricting cycle was in effect.

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In some posts to follow, I’ll offer some suggestions about the potential implications of this trend, and examine the pattern since the last redistricting cycle.   Five states are not yet included in my dataset, but the overall average for GOP held districts is somewhere in the 13%-15% growth range, whereas Democrats are closer to 2%-4%.  About 1/4 of districts lost population in this period, and 2/3 of these are Democratic.  About 1/5 of districts grew by 20% or more, and 4/5 of these are Republican.  Similar tendencies appear for the U.S. House.  The trend follows from widely documented growth in red states and suburbs.

The typical reaction says the trend, if it means anything, confers some kind of advantage to Republicans.  Maybe that’s true, but it also suggests the possibility that Republican held districts are changing and their constituencies are less stable.  What does the variation of district population growth tell us? The next several posts will examine some descriptive data and test a few possible outcomes.  Population growth is a relatively easily obtained metric, and some of its lessons may be hiding in plain sight.

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