Temping thought Dave. The other thought that occurs to me is that maybe those voting were all members of the Institute of Actuaries, clustered around a laptop computer during a day's outing, or a conference break. If so, pleasure to have them on board!

Nic, maybe we should just ask the (currently) 6.6% of respondees to publish thier pages of calculations.  The rest of us poor mortals can then try and decipher them.

Thank you for that very useful comment. The problem relates to the point from which interest is calculated. There are, from memory, six different ways, which can have a significant impact on the amount you pay. The difference, even with the same APR, can be as much as 70% between the cheapest and most expensive.

A few years ago, the Treasury Select Committee (a parliamentary group of MPs) engaged a Cambridge University maths professor, Robert Hunt, to try to untangle the charges on just one card, and relating to a very simple set of transactions over one month. It took him several hours and many pages of A4 working out all the formulae - and he still professed himself not 100% certain about his end result.

Imagine how long it would take to work out all six sets of different charges!

Hi there,

I just followed some basic maths on my latest credit card statement and the whole thing is a mystery.

Despite quoting a monthly interest rate of 0.79%, the actual interest worked out to be nearer 1.355% per month.

This rounded up to an annual interest rate of 16.25% instead of the 14.9% advertised. I'm sure that the equation is a lot more complex than my basic percentage-based maths, but I do think a lot more transparency is in order.