Estimating the seigniorage tax

Chart from Menzie showing ten year yield forecasts. 

The forecasters vary as the lower chart  showing the tax. But they seem centered about 1.5%. Over the long term it seems the ten year is settling to 1.5.

  

But the lower chart  shows a hard bound on that tax.  It looks jagged at the end, like a  pitchfork. That is a fitting metaphor.