Lousy definition

R-star is what economists call the natural rate of interest; it’s the real interest rate expected to prevail when the economy is at full strength. 

R-star really is the  rate  of surplus accumulation needed to compensate for  expected tail losses.  The uncertainty of trade yield a distribution, and some small part of that will be losses. R-star is an insurance function, it is measured over time, so it compensates when bankers get 'time to completion' wrong.. 

In my definition set, this number is close to bit error, and a half point seems right. The Fed jumps around in quarter points, trying to stay ahead. If NGDP at risk  is five points, then I get something like a rank five generator,  I can construct the central bank currency function in a spreadsheet macro.

The variations within the sequence  is price uncertainty, not R-star, it is the business of banks to create the best generator of that price variation. Then the have a model of real transactions queued in the currency zone.