How often the Universe has planets truly like the earth - true earth twins, planets the size of the earth, rocky planets with a surface that supports liquid water - well, we don't have that number yet, but I'm optimistic we'll figure it out.

BBC: From counting to characterising exoplanets

And if that analysis was correct for the ten-year Treasuries that Mr Kat and his colleagues looked at, it is even more true for 30- or 50-year bonds which may, in addition, be less liquid.

ECONOMIST: Buttonwood