This is a very good object lesson on why starting points matter when making time series comparisons, especially cross-sectionally:
But is Iceland’s post-crisis “miracle” real? No. It is an illusion created by the starting date Krugman chose for his figure. If we shift it back just one quarter – the quarter before Latvia and Estonia’s GDP peak – Iceland’s performance no longer stands out...
Iceland’s massive devaluation improved the country’s trade competitiveness, while imposing huge losses on its krona-based savers. Ireland’s inability to devalue protected its citizens’ euro-based savings, but has forced it to improve competitiveness in other ways, such as through wage cuts. Of the lessons that can reasonably be drawn from Iceland’s experience over the past decade, the benefits to tiny statelets of having a currency to debase is hardly one of them.
Graphs and more analysis at the link. One lesson is that a whole lot of time series stats are questionable, especially those coming from partisan think tanks or public ideologues. Another is that sometimes it's really hard to make appropriate comparisons, because choosing a starting date is arbitrary by nature. I don't mean to pick on Krugman here (this time) because I don't think he's doing anything intentionally wrong. The point is to be careful when producing, or consuming, statistical information.