https://blogs.ucl.ac.uk/brits/2014/06/01/worksheet-3-scenario-analysis/?unapproved=71356&moderation-hash=7b4c72b6a1317b4b80c119188b32b39f#comment-71356
https://blogs.ucl.ac.uk/brits/2014/06/01/worksheet-3-scenario-analysis/?unapproved=71356&moderation-hash=7b4c72b6a1317b4b80c119188b32b39f#comment-71356