For policymakers, this a crucial point: Given the real-time data problems with which they are confronted, looking at monetary developments may be useful for learning about the current (and future) state of the economy even in the New-Keynesian world which, at first sight, has no such role for money to offer.
And this point is to some extent also related to Wicksell’s theory, where an interest rate gap has direct implications for credit and money growth. I will come back later to the issue of monetary indicators’ usefulness.