But if such tensions are not eased and the lack of jobs and opportunities not addressed, Ethiopia's future could get much bumpier.

ECONOMIST: Ethiopia

But the decline is a lot bumpier than the rise: the pH difference from one year to the next is frequently greater than the change in average pH levels over 20 years.

ECONOMIST: Ocean acidification

"The eventual exit from exceptionally loose monetary policy could make the recovery in the housing market bumpier than some might expect after the last few months of price increases, " said Mr Gahbauer.

BBC: House prices 'continue to rise'