It could be £24 billion. It could be £47 billion. It might even be £100 billion. The pension funds of the UK’s local governments make one of the world’s largest pools of public pension assets but assessing the size of their total deficit remains a mixture of science and guesswork.

The schemes manage £226 billion in assets. If combined they would manage more than Calpers, the largest public pension fund in the US. But combined they are not. A Financial News analysis shows deep variations in how they measure their deficits, driven by their choice of actuarial consultant.