State Legislatures: Odd or Even?

After my project a few weeks ago of Senators Per State Since 1959, I have now returned to state-based mapmaking. The idea for this map came to me totally out of nowhere: Out of the fifty state legislatures in the United States, which ones have an odd number of members, and which ones have an even number?

I quickly realized I should break the question down even further, according to each chamber of the legislature. Since 49 of the states are bicameral, this made it simple to make a Punnett square of the four combinations possible with an odd or even house and an odd or even senate. Look at the results for yourself:

Now, an odd or even number of politicians in each state's representative body may seem like a completely random data set to analyze. Indeed, the results shown on the map would seem to say as much, as there are few easily graspable patterns. No region of the country is characterized by a single set-up: not New England, not the Deep South, not the Great Plains, not the Pacific states, nor even the Four Corners states. However, in the course of my rapid Wikipedia research, it is readily apparent that different states legislatures very much influenced each other. Many states' chambers are not called the "house" (lower) and "senate" (lower) as in the U.S. Congress. For example, the lower chambers in Maryland, Virginia and West Virginia are known as the "House of Delegates," the legislatures of Vermont, Rhode Island and Connecticut are called the "General Assembly," and the lower chambers of California and New York are both called the "State Assembly." I don't think those are coincidences.

In addition, while none of this map's results fit with usual regional categories, there are certainly groupings with the same oddness or evenness. The odd house and even senate is the least popular set-up, (besides lonely unicameral Nebraska), but the odd-even match has two tight groupings of three states each: Oklahoma, Kansas, Missouri, and Pennsylvania, Connecticut, Rhode Island. The next least popular choice, the even house and odd senate, also has interesting characteristics: only one has any coastline (Texas) and all are west of the Mississippi and border at least one other state of the same combination - except for Illinois. There are fifteen states whose legislatures have an odd number of members in total (including unicameral Nebraska).

Thus, the clear majority of states have an even total of legislators, but they are split between even-even and odd-odd. (Even-even wins as most popular, with 22 adherents.) Certain pairs of states that might otherwise be grouped together are divided along these lines, like Washington and Oregon and Mississippi and Alabama. Alaska and Hawai'i, so united in terms of their age as states, their geographic separateness, their strong indigenous cultures and attractiveness to tourists, are also split according to this division. So what does it matter anyway, whether state legislatures are odd or even?

A body with an odd number of members might seem more likely to avoid ties. However, one abstention or absence can easily ruin that, and how likely is it anyway that a group with dozens or even hundreds of members will end up tied? Some states allow for variance in their number of legislators; it would be interesting to see which do and why. (If I remember correctly, Maine, New York and California are among them.) One particular set-up might indicate a certain power dynamic between chambers: I would say that in even house/odd senate states, the senate has greater powers, because it must be seen as critical that the senate doesn't tie. (I'm probably wrong, but it's just a hypothesis.) Overall, I think this study serves as a rudimentary indicator of wider similarities and patterns connecting the state legislatures of the United States. In upcoming maps, I believe I will explore considerations that are more relevant to actual political function, such as the number of legislators in each state, or the ratio between numbers in the house and senate.


  1. Wow! Interesting idea for a map! I have never thought of that...


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