At the moment you have finalised your spend analysis and bundled your purchasing items into commodities or Sourcing Groups, you might find this excel spreadsheet useful to identify which ones are the most appropriate to go through a complete strategic sourcing methodology.
Nothing fancy here, only pragmatic factors about markets, suppliers, products and ‘buying’, sorted in a .xls table to review and weight per Sourcing Group. The more points you give to a Sourcing Group the best it is. An example is attached. Hope it helps.