How much should our public representatives be paid? This simple question always stirs up emotion and controversy wherever it is asked. In an age of austerity it carries particular resonance and is but one part of the much bigger debate over pay levels in the public sector generally. Ministers and TDs would undoubtedly say that they have been leading by example, taking significant cuts to their pay and perks. Others, no doubt, have different opinions about the amount of leadership that has been on offer.

Over in the UK, MPs pay is very hot topic. It's not just about austerity: a previous scandal about abuse of expenses and allowances still rumbles on. A very grand sounding official body called the Independent Parliamentary Standards Authority (IPSA) has recently tackled the thorny question of how to justify the next salary increase for MPs. Actually, that's not what they set out to do, so my description is a little unfair. The men and women of IPSA took a very thorough look at the whole area of pay, perks, pensions and pay-offs, thought very hard about it all, and then recommended a pay rise.

It’s a tough question. Normal laws of labour supply and demand don’t seem to apply to Parliamentarians. Some of us might wonder what laws do. This is what IPSA has to say about the job market for MPs:

“Many of the tools used in other walks of life to determine pay are not available to us when considering MPs’ remuneration, such as data on recruitment and retention. MPs have no job description. They do not have to undergo training or gain qualifications. They have no annual appraisals nor performance reviews completed by their line managers. Indeed, they have no line managers. The argument is made, and it is a fair one, that the role is unique.”

Now, I may be at completely the wrong end of the stick here, but I am not sure what part of this statement stands up to more than a second or two of scrutiny. No data on recruitment and retention? I respectfully refer IPSA to historyofparliamentonline.org. And, indeed, many other histories of English and UK parliaments that seem to send a similar message about the potential supply of MPs. There are always large numbers of people wanting to be one. And no matter what they are paid, they still keep knocking at the door. And usually get in if they went to Eton and Oxbridge.

IPSA reckons that MPs have “no job description”. I would guess that the electorate would have something to say about that. Or maybe not; if MPs have nothing to guide them through their parliamentary life, it is no wonder that so many of them end up looking more than a little lost. But are we really to believe that nobody knows what it means to be an MP? Again, the electorate does from time to time have something to say about performance. And I would have thought that some kind of appraisal system was operated by party leaders and the whips.

IPSA do provide us with some great data. They find huge variation between countries, with plenty of surprises. Irish TDs are paid a bit more than their UK equivalents, at least in terms of base salary. Spanish law makers seem to be a pretty austere bunch but those in Italy are paid multiples of their Spanish counterparts.

While I might quibble with IPSA’s methods and conclusions, they do seem to have tried hard. Their report illustrates perfectly how there is no right answer to our question. Where the laws of supply and demand break down, we have nothing suitable to replace them. And that goes for large swathes of the public sector. IPSA will remind some readers of the benchmarking exercise that so inflated Irish public sector pay back in good old days. In the private sector, the presence of “remuneration committees” that set board room pay are also often a simple device for boosting salaries.

Here’s a suggestion for the next time this argument erupts - whatever the job, teacher, nurse or TD, use the median pay level in the euro zone as the benchmark. It will keep things very simple.