Not trying to back any specific side here, but the divergence at 2013 is because they're using a difference in price relative to Q1 2013 (so near 2013 it will always be close to zero). If you used 2015 or something the right graph would still look similar. We don't know if such a divergence is present since the 1980s since no data is presented (making it an unhelpful comparison).

It would also be good to see more countries included, and the actual lines labeled for which country they are. Overall I would say this graphic doesn't provide adequate information to back up its claim.

Also as Onomatopoeia@lemmy.cafe said above, different counties have different markets, policies, economies, etc. making it hard to make generalizations.