The Senate of the US has two members for every state. That's right out of the Constitution. But there's no direct guidance for how big the House should be, except for a ceiling of no more than one Representative for every 30,000 citizens, which would mean about 9300 Representatives.
Obviously we don't have that many, and the reason is that quite a while ago it was recognized that as the chamber became larger it also became more unwieldy, and so the House itself capped its numbers at 435. What if it got larger?
It won't. The House itself decided that it is now a zero-sum game. Every ten years at the census, there's always one or two states who will lose a representative to some faster-growing state, and goes to court to try to prevent it (usually by trying to claim some sort of undercount). Generally the courts have been quite unsympathetic to these cases. But no one tries to "solve" the problem by increasing the size of the House, because if that ever happens the dam will be broken and it will flood totally out of control. How can you actually get anything useful done even in a chamber of 435 members? (The unkind would argue that the House proves that you can't...) How could you if it got even larger?
The evidence from history is that when these kinds of chambers reach a certain size, membership in them becomes more symbolic than meaningful. As a practical matter, you get a relatively small group of members who wield most of the power, and that's what happens in the House. As a practical matter, the political party in the majority controls all the important committee chairmanships and selects the Speaker, and through that keeps the House from grinding to a halt under the weight of numbers. There's a reason why the House Majority Leader is important.
One wonders just what the European Parliament will do about that same problem. With new states entering the Union, the idea of existing members losing seats to the new entries seems to not have been acceptable. Thus on May 1, 162 new members were added to the Parliament, bringing its total up to 788.
Think about this: if the chamber were debating a highly critical issue, and if every member chose to give a 5 minute speech, it would take nearly 66 hours to get through them all. Which as a practical matter means that most of those members won't matter. It isn't possible for them to matter.
These new members aren't full voting members, yet; they'll become voting members when their home nations become full members of the EU. But this clearly opens the question of what Europe intends to do in the long run about Parliamentary representation of the various member nations as the result of demographic shifts. If, in the course of some sort of European census, it becomes clear that some nation has grown a great deal and some other nation has had a decline in population, will they adjust the number of Parliamentary seats? And if so, will they do it by adding seats for the growing nation without taking seats away from the one that is in decline?
It doesn't seem likely that they would do what the House did, and to cap their own numbers and to actually accept that this means that some states will lose members as the result of demographic changes.
But it's not clear it really matters anyway; under the kinds of proposals being made for the EU, the Parliament is nearly meaningless. On the global scale of significance, it's only going to rate about two steps above the UN General Assembly.
