US House size increase: Inherently valuable?

We have frequently discussed here the question of the size of the US House. As regular readers will know, the House is undersized, relative to the cube root law, under which an assembly is expected to be approximately the cube root of the population. The law is both theoretical (grounded in a logical model) and quite strong empirically (see the graph posted years ago). However, the US House is far smaller than the cube root predicts, which would be somewhere north of 600. In fact, the House has been fixed at 435 for more than a century,1 even as the population has grown greatly.

So there is a good political science case to be made for expanding House size. My question here is whether expanding the House is something that reformers should pursue for its own sake. Or is it of subordinate value?

I ask because many advocates of a move to proportional representation (PR) will tend to believe that PR would work better in a larger House. The larger the House, the fewer states there are with only one Representative, wherein obviously a plurality or majority system remains the only option.

Strategically, however, it could be a mistake for the PR movement to hitch its wagon to the House expansion movement. If PR is attached to the idea of “more politicians” it is probably in a lot of trouble. Advocates for democracy reform might prefer both a larger House and PR, but wouldn’t most of us prefer PR to a larger House, if we can have only one or the other? (Perhaps I will engage in blasphemy, but I might trade off a somewhat smaller House if it were necessary to get PR. In other words, I value PR ahead of almost any reform I can imagine.)

Another way to look at this is, would the reformist “capital” spent on getting a larger House be worth it if we ended up with 650 single-seat districts instead of 435? I have my doubts.

While a larger House should result in more parties represented, independent of the electoral system, I am not sure I believe that we would see it under otherwise existing US political and institutional conditions. As I’ve noted many times, the Seat Product Model says that the US “should” have a party system with more than two parties, and the largest one averaging around 47% of the seats, instead of our actual average which is obviously greater than 50%. It should have an effective number of seat-winning parties of about 2.75, even with 435 seats. With 650, the expectation rises to 2.94 (and a largest averaging just under 45% of the seats). In the real USA where there are really only two parties, and we keep single-seat districts, do we have any reason to believe just adding about 200 seats (let alone a more realistic 100 or so) would result in any increase in representation of other parties? I doubt it.

So, why bother? Is the value of a smaller number of people per Representative so strong that we want it regardless of how the party system pans out? I worry it actually could have a deleterious effect. Other things equal, more seats means more homogenous districts. Some of those could be minority districts that can’t now be drawn (given other criteria in district line-drawing) and, of course, those minorities in theory could be minority-party supporters as well as nonpartisan minorities (racial and ethnic, etc.). The latter is valuable, of course. But a concern is that in an existing and likely persistent two-party system that you simply end up with more safe seats (Brian Frederick notes this possibility in his book on US House size, even as he argues in favor of an increased size). We have plenty of safe seats already! If we had multiparty politics to start with, I think a larger House would help smaller parties win more seats, and possibly render districts on average more competitive. But in a two-party system, I think it makes districts on average less competitive. (I am not sure about this, so discuss away in the comments!) As for racial and ethnic minorities, I am skeptical that we get enough of a boost from a larger number of single-seat districts to make the tradeoffs in less competitive elections worth it. They’d be better represented by PR anyway, obviously.

Bottom line: With so many reformist needs in US democracy, I don’t think House size is worth pursuing, unless it can be in a package that gets us PR. It certainly should not be allowed to be the poison pill that prevents getting PR, as I fear it could be, were we ever otherwise in a place where PR was a live option.


  1. Except for temporary increases to accommodate Alaska and Hawaii; at the next census and reapportionment, it reverted to 435.