Analysts and strategists assessing whether there’s an economic recovery on the way are increasingly referring to “second derivatives”. It usually means a measure, say production, has declined, but not by as much as it did last month, or quarter.

Are second derivatives a strong basis for optimism? If you have to perform differential calculus to make a point, it may be a sign of desperation.

Equities markets continue to factor in a recovery, with the FTSE 100 up about 30 percent from its six-year low of March 9.

Yet the economic data does not support this view.

Look at production figures from most major economies over the last few months, for example. You will see them in decline, month by month. It will be a series like:

200, 188, 173, 160, 151

The data won’t necessarily form the neat curves we know and love from our knowledge of differential calculus. But the principles are the same.