Productivity. It's hard to measure. It depends on measuring inputs and outputs and then comparising the two. If outputs rise more slowly than inputs, then productivity is falling. Stay awake at the back there.
But what are the inputs in public services? Cash? That's not a very good measure when what you're putting in keeps moving between different accounting heads within a massive behemoth like, say, the National Health Service. Numbers of staff? Also not very logical - is a doctor worth two or a nurse, or less than one of a nurse? I'm not sure, and I'll willing to gamble that no-one else is either. And what about the outputs? Patients treated? For what ailments? Waiting list times? What will the cut-off times be and the units of measurement? Days? Weeks?
It's all a bit of a conundrum, really.
The issue which makes all this important - rather than of interest to dry-as-dust academics like me - is that 'falling NHS productivity' has been used to justify present Health Secretary Andrew Lansley's (above) current dog's dinner of a reform package - a turd so difficult to polish that Conservative Cabinet Ministers and Downing Street insiders wish, over and over again, that it would just go away.
The idea that the NHS has 'wasted billions' has been elevated recently to something of a mythic truth - an unchallenged shibolleth that has helped to bring Labour, social democracy and socialised medicine itself into disrepute.
But news arrived yesterday of the uncertain intellectual and statistical foundations of the idea. Published in The Lancet (subscription may be required), of all august places, the latest modelling shows that if we tweak thinks a bit, and put a bit more emphasis on morbidity and mortality (surely what we all worry about most), rather than on admissions and consultations, productivity has been rising - and pretty strongly - since the early 2000s. Top Department of Health officials have reportedly been surprised. If they knew their history and their economics, they wouldn't have been.
Now I'm not enough of an expert to know quite who's right. But even under the old figures, real terms money increases going in had been rising by 5.9 per cent a year, while 'outputs' had been rising by 5.5 per cent a year. That's even assuming that the NHS is a 'I want to see a specialist doctor' service rather than a 'I want to live and not be in pain' service. So productivity had been falling rather gently, if at all - every extra pound bought over 'ninety pence' of extra doctor visits to your ward.
You know what? Between 2001 and 2010 - between Tony Blair's commitment to raise British health spending to the European average and the moment when his party was booted out of office - the NHS got better and better and better. It attracted record levels of satisfaction; it basically abolished waiting lists. Understanding and embracing this fact totally destroys the case for the 'big bang' reform the NHS is now being subjected to.
Don't let anyone tell you any different, will you?
