When Peter Robinson stands down in a few weeks' time as an MLA for East Belfast a member of the DUP will be appointed to take his place. We don't have by-elections to the Assembly: partly because they would be enormously difficult in a multi-Member constituency using the single transferable vote method; partly because of the expense involved; but mostly because it might upset the delicate political balance.
In other words, if Alex Attwood, the SDLP's only member in West Belfast, had to stand down due to ill-health it would be almost impossible for the SDLP to hold the seat in a by-election to replace him.
When Robinson's successor is appointed it will bring to 22 the number of MLAs who have been co-opted in the lifetime of the present Assembly. Include the fact that Basil McCrea, John McCallister and David McNarry do not have a mandate for their present political designation (all three were elected as UUP candidates) and you have 25 MLAs - almost a quarter of the total - who don't have a mandate.
You didn't elect them. I didn't elect them. In some cases they weren't even selected by members of their own constituency association.
If the same rules and circumstances applied across the rest of the UK - which they don't, of course - it would mean that 32 out of 129 Members of the Scottish Parliament (MSPs) and 15 out of 60 Members of the Welsh Assembly (AMs) would be unelected. And 150 out of 650 MPs in the House of Commons.
Scotland has 129 MSPs - 73 directly elected "constituency MSPs" in single-Member constituencies and the other 56 "list MSPs", chosen as part of a list system of seven Members per eight regional electoral areas.
In the lifetime of the present parliament there have been three by-elections to replace constituency MSPs, two of whom died and one who had to resign after being convicted of assault.
Four of the list MSPs have been replaced after two died, one won a by-election and the other took up a job with a trade union.
In the Welsh Assembly, which has a similar electoral system, there has only been one by-election, to replace a Member who left politics altogether.
Does it matter that so many MLAs don't have a mandate? Of course it does: by-elections are important. They allow us to pass judgment on the work of the Executive. They allow us to pass judgment on a particular party.
They are better than opinion polls. They encourage debate. They encourage independent voices and smaller parties. They are good opportunities for genuine opposition voices.
It stops the political/electoral Establishment taking us for granted. It shakes up things, which is a necessary part of political accountability.
And, when all is said and done, the bedrock of democracy is that we elect our representatives. We might not like how they vote on key issues, but at least we know they have a mandate to be making those decisions.
Now, given the general perception of MLAs as overpaid indolents in an Assembly that doesn't seem to do very much, the presence of so many without a mandate to be there does nothing to inspire confidence.
And the accompanying suspicion that some of them have been co-opted to give them time to warm up the seat, boost their profile and increase their electoral chances, merely adds to public cynicism.
For instance, is there any particular reason why Peter Robinson couldn't have remained as an MLA for the next few months, with the Assembly mandate due to expire in a few months anyway? There are also rumours of two other MLAs preparing to step down within a matter of weeks to give their successors a better chance of retaining the seat.
A system that doesn't require by-elections is a system that is open to abuse, and open to the sort of manipulation that allows parties to play musical chairs, or move people about for their own internal advantage.
It also encourages parties to become as bad as each other, using the pretence that "we're not afraid of elections, we're just not allowed to have any".
In South Belfast, for example, four of the six MLAs have been co-opted. In East Belfast it will soon be two of the six: meaning that half the MLAs in those two constituencies have no mandate to be in the Assembly. That is plain crazy.
So, is there a way round it? Well, we could begin by changing the rules and saying that by-elections should be permissible in some circumstances.
The notion that a Member should be encouraged to step down simply to make it easier for a potential successor should also be discouraged. In other words, you step down at your peril.
A Member who chooses other employment, or who is forced to resign for "personal reasons", must make that choice against a background in which the resignation will result in a by-election.
MLAs seeking election to other bodies would think twice if they had to resign in advance knowing that their resignation would lead to an immediate by-election.
Rules don't exist to make it easier for parties to keep seats - especially if they can keep them without the chore of actually fighting for them and winning them.
I would - although I'm still open to persuasion - make exceptions in the case of death or for a sudden and potentially long-term illness or disability that made it impossible or extremely difficult for the MLA to do their job.
But in every other circumstance there is no solid reason why there shouldn't be a by-election.
Yes, it would require funding, but that's also the case for Scotland, Wales and Westminster (and I'm pretty sure MLAs wouldn't be chopping and changing with such regularity if they knew it would lead to by-elections).
And, yes, it might lead to parties (the SDLP in West Belfast or UUP in East Belfast) losing their only seat, but so what? That's the way the cookie crumbles in politics.
Again, the rules shouldn't be about protecting individual parties from electoral realities.
Also, while electing just one Member in a multi-Member constituency could lead to problems of one sort or another, it strikes me that none of those potential problems are insuperable.
Whatever its faults, the Assembly represents democracy.
Its Members are elected to represent our interests and to govern Northern Ireland. Is it really too much to expect that those Members be elected, or that they have a specific mandate to make those decisions on our behalf?
Democracy can be uncomfortable for some parties and elections can produce results they don't like. So be it. Democracy and the electorate are much, much more important than the self-preserving interests of individual parties.