The equation of equality.
You know how it is. When it comes to leagues - of wealth, productivity, employment, the health of the nation - Wales is usually languishing towards the bottom, if not at the very bottom of statistical leagues.
There is one, however, where we're out in the lead.
We might represent just 5% of the UK wide population but 6.2% of all MPs represent Welsh constituencies.
8.6% of the population live in Scotland; they have 9.1% of all MPs.
In Northern Ireland the comparable figures are 2.5% and 2.8%.
But in England? 83.9% of the electorate are represented by 81.9% of all MPs.
When David Cameron first came to the National Assembly some time ago, he'd got on to the subject of cutting the number of MPs in Wales even before we sat down to conduct his interview. With only the slightest prompting from me he made clear that this was one cut he's not only happy to talk about but is intent on following through. Cut the cost of politics, cut down the menu in the House of Commons offering "lean salad of lemon and lime marinated roasted tofu with baby spinach and rocket" for under a couple of quid and more significantly, cut back on the number of those politicians you're so enamoured with. Reduce the number of MPs in Westminster and save some £15million while you're at it.
How deep does this particular cut go? How many MPs will face the axe? What Mr Cameron has said in the past is that he'd ask the Boundary Commission to consider how to cut the number of MPs by 10%.
650 MPs become 586. By my maths 40 Welsh MPs become 36. Simple? No.
A few points.
If we in Wales currently had the same number of MPs per head as England, we'd wake up to find we had 32 MPs, not 40. That would be before any further, more general cut in the number of Westminster politicians.
If a10% cut were then to be made to that level political playing field the Conservatives want, that takes you to some 29/30 Welsh MPs.
Point number two.
Woudl there be a knock-on effect on the National Assembly? Yes, there would be. Under the Government of Wales Act 2006 two thirds of AMs are elected to represent constituencies that follow the same boundaries as Westminster constituencies. The Government of Wales Act would have to be amended then, or there would be a cut in the number of AMs too. The boundaries of Assembly and Westminster constituencies would in future differ, just as they do in Scotland where the number of MPs has already been reduced from 72 to 59.
The reduction there came after the referendum that granted substantial primary law-making powers to the Scottish Parliament. Is that regarded as a precedent by the Conservatives? It's not clear.
Throw in what is know as the "Stormont Discount" - I won't go into it here but applying it would mean Welsh, Scottish and Northern Irish MPs would very rarely vote on issues that only directly affect England - and academics who've long focussed on this issue can foresee a future where Wales has just 21 MPs. (One of those academics spells out the implications of the Stormont Discount as he sees it here. The article is in Welsh.)
Likely? Come off it but on paper, if not politically, not impossible they argue.
So 36 MPs, 32 MPs, 29 MPs, 21 MPs ... take your pick. Which way are we headed?
Take a look at the Conservative manifesto launched yesterday and what does it actually say? Turn to p.67.
"A Conservative government will ensure every vote will have equal value by introducing 'fair vote' reforms to equalise the size of constituency electorates, and conduct a boundary review to implement these changes within five years."
'Fair vote' reforms. What will that mean?
If you follow the logic of 'fair votes' doesn't that sound like a cut of 10% in the number of English MPs (down to 36 in Wales) then equalise the number of MPs per head in England and Wales to make it 'fair' and that brings you down to some 29/30 MPs.
Is that where we're headed if Mr Cameron makes it to Number Ten?
The Conservatives aren't saying any more. They've never set a figure on the number of Welsh constituencies that will survive the cuts; they'll hold a boundary review. That, for now, is all they'll say.
With their Welsh manifesto launch imminent, what are the chances they'll say some more?