How deep the recession?

To estimate just how deep the covid crash will be, I created an index of all the PMIs (purchasing managers' indices) which covered the GFC recession (2008/2009).  In some cases, the PMIs from IHS Markit (or at least my data) don't go back far enough, but there are similar surveys available.  For example in South Africa, there is a survey by ABSA (a bank), in India a survey of business expectations.  The component countries make up 61% of world GDP.  I included PMIs for services (non-manufacturing) where available even though I usually don't (because the main driver of the business cycle is usually manufacturing).  This time however, the downward impulse is driven by the collapse in services.

The index is based only on data which are available.   For example, we don't have a PMI for China for March, nor for several other countries in the index.  So the March data point of my index is likely to be lower when we get them.

However, based on the data we do have, the current recession is already likely to be deeper than the GFC.  Assuming an 8 week shutdown with a cautious re-opening afterwards, world GDP  will prolly fall in Q1 and Q2, and start a gradual recovery thereafter.  At its low point, world GDP will likely be down more than 5% year on year.

Underlying data sources: various.
My calculations of world GDP and long series PMI, using PPP GDP weights.