Why can't we achieve price stability with a coin cap? This way the supply of money is 100% predictable simply because it's set in stone. Markets like consistency(predictability) which gives markets confidence and hence leads to price stability.
Agreed that consistency is important. A known rate of increase is exactly as predictable as a cap.
Another aspect is that the population is always growing. Again, that too is predictable but if the population grows faster than the money pool that necessarily drives prices down—it's a constant forced deflationary policy which, while predictable, distorts value, and I see that as being just as bad as a constant inflationary one. Balancing the money supply with the population growth is a small measure compared to other factors, but if all other things were equal, a 1% per year increase in the money supply would be the best policy. It's a point that reasonable people can disagree on and the fact that there are so many other factors at play means it would be very difficult to prove one way or another.
Setting aside my own belief and opinion about money policy, what is more relevant to the original question is: does the constant and predictable inflation built in to PPC (I'm not as familiar with XPM) make it "keynesian" in nature. Considering that so-called keynesians like to manipulate the money supply on a year-by-year basis to "steer" the economy, as well as the fact that the "keynesians" I'm most familiar with (economists and politicians in the United States) are increasing to the money supply by 5%-8% per year, I'd say no. "Keynesians" want to be able to adjust the rate at will (which is not the case with PPC) and they want to increase the money supply much faster than the population is growing.
So even if you disagree with me about the desirability of a 1% increase in the money supply, I think it is fair to say that a steady and predictable 1% increase per year is very far from "keynesian" and at the very least much less damaging than current "keynesian" policy.
