One thing that is also important about Wicksell's rule is that if the yield curve is negatively sloped (the bank rate is higher than the natural rate) then a recession (deflationary forces) are to be expected. The graph below uses the Fed Funds for the bank rate and the 10 year Treasury bond rate for the natural rate. In between the gray lines the official NBER recessions are shown.
As it can be seen, after the red line (Fed Funds) moves above the blue line (Treasury bonds rate) a recession always follows. There are many problems with the Wicksellian model, not the least the assumption of a natural rate of interest, that was severely criticized by Keynes in the General Theory. But the empirical notion that an inverted yield curve forecasts a recession seems to survive any possible theoretical critique. More on the critique will be left for other posts.